Each figure in both manuscript and SI has its own folder. Filenames describe which part of the figure the data is for; where there is more than one file for a figure, further details are given in the filename. All files can be opened in txt files; .cif and .mcif files can also be opened in software designed for viewing crystal structures. Information about data collection and analysis is given in the manuscript and SI. Folder contents Manuscript Figure1 Figure1c.cif - this includes the complete crystal structure for Dy3Mg2Sb3O14 (same as SIfigure1b_structure.cif); only Dy and Mg positions are shown in Figure 1c. Figure1d_ZFCchi_invchi.txt - ZFC susceptibility and inverse as a function of temperature. Figure1d_FCchi_invchi.txt - FC susceptibility and inverse as a function of temperature. Figure1e_MH5K.txt - isothermal magnetisation measured at 5 K. Figure1e_MH15K.txt - isothermal magnetisation measured at 15 K. Figure1e_MH30K.txt - isothermal magnetisation measured at 30 K. Figure1e_MH60K.txt - isothermal magnetisation measured at 60 K. Figure2 Figure2a_CpoverT_0T.txt - Cp/T as a function of temperature collected in 0 T field (same as Figure3d_experimental.txt and SIFigure5.txt). Figure2a_CpoverT_0p5T.txt - Cp/T as a function of temperature collected in 0.5 T field. Figure2a_DS_0T.txt - magnetic entropy as a function of temperature in 0 T field. Figure2a_DS_0p5T.txt - magnetic entropy as a function of temperature in 0.5 T field. Figure2b_0p5K-50K.txt - intensity at 0.5 K minus intensity at 50 K as function of Q, collected on DCS at NIST (same as SIFigure7_DCS_0-5K-50K.txt). Figure2b_0p03K-50K.txt - intensity at 0.03 K minus intensity at 50 K as function of Q, collected on DCS at NIST (SIFigure7_DCS_0-03K-50K.txt and SIFigure9_DCS_0-03K-50K.txt). Figure2c_0p03K-0p5K.txt - intensity at 0.03 K minus intensity at 0.5 K as function of Q, collected on DCS at NIST. Figure2c_magstructure.mcif - average magnetic structure of Dy3Mg2Sb3O14 obtained from analysis of data in Figure2c_0-03K-0-5K.txt. Figure3 Figure3a_orderedmoment_Rietveld.txt - ordered moment per Dy obtained from Rietveld refinement as a function of temperature for Dy3Mg2Sb3O14. Figure3a_orderedmoment_MC.txt - ordered moment per Dy calculated from MC simulations with 4% disorder as a function of temperature. Figure3a_pm3triangles_RMC.txt - % of triangles with +/-3 charge obtained from RMC refinement as a function of temperature. Figure3a_pm3triangles_MC.txt - % of triangles with +/-3 charge calculated from MC simulations with 4% disorder as a function of temperature. Figure3b_0p5Kpositive.txt - positive charge correlations obtained from RMC refinement at 0.5 K. Figure3b_0p5Knegative.txt - negative charge correlations obtained from RMC refinement at 0.5 K. Figure3c_0p03Kpositive.txt - positive charge correlations obtained from RMC refinement at 0.03 K. Figure3c_0p03Knegative.txt - negative charge correlations obtained from RMC refinement at 0.03 K. Figure3d_experimental.txt - Cp/T as a function of temperature collected in 0 T field (same as Figure2a_CpoverT_0T.txt and SIFigure5.txt) Figure3d_MC_nodisorder.txt - Monte Carlo simulation of Cp/T for 0% disorder Figure3d_MC_0p02disorder.txt - Monte Carlo simulation of Cp/T for 1% disorder. Figure3d_MC_0p04disorder.txt - Monte Carlo simulation of Cp/T for 2% disorder. Figure3d_MC_0p06disorder.txt - Monte Carlo simulation of Cp/T for 4% disorder. Figure3e_RMC.txt - Simulated neutron scattering for Dy3Mg2Sb3O14 at 0.03K obtained from RMC. Figure3e_MC_nodisorder.txt - Monte Carlo simulation of neutron scattering for Dy3Mg2Sb3O14 with 0% disorder at 0.2 K. Figure3e_MC_0p01disorder.txt - Monte Carlo simulation of neutron scattering for Dy3Mg2Sb3O14 with 1% disorder at 0.2 K. Figure3e_MC_0p02disorder.txt - Monte Carlo simulation of neutron scattering for Dy3Mg2Sb3O14 with 2% disorder at 0.2 K. Figure3e_MC_0p04disorder.txt - Monte Carlo simulation of neutron scattering for Dy3Mg2Sb3O14 with 4% disorder at 0.2 K. Figure3e_MC_0p06disorder.txt - Monte Carlo simulation of neutron scattering for Dy3Mg2Sb3O14 with 6% disorder at 0.2 K. Supplemental_Information SI_Figure1 SIFigure1a_NPD.txt - intensity as a function of d for Dy3Mg2Sb3O14 from bank 5 on the GEM diffractometer at ISIS at 300 K. SIFigure1b_XRD.txt - intensity as a function of d for Dy3Mg2Sb3O14 collected on a laboratory X-ray diffractometer at 300 K. SIFigure1b_structure.cif - crystal structure for Dy3Mg2Sb3O14. SI_Figure2 SIFigure2_25K.txt - intensity as a function of d for Dy3Mg2Sb3O14 from bank 5 on the GEM diffractometer at ISIS at 25 K. SIFigure2_0p05K.txt - intensity as a function of d for Dy3Mg2Sb3O14 from bank 5 on the GEM diffractometer at ISIS at 0.05 K. SI_Figure3 SIFigure3.cif - crystal structure for Dy3Mg2Sb3O14 from which bond lengths and angles have been determined. SI_Figure4 need data - SIFigure4.txt - momentum versus energy transfer at 0.03 K collected on DCS at NIST. SI_Figure5 SIFigure5.txt - Cp/T as a function of temperature collected in 0 T field (Figure2a_CpoverT_0T.txt and Figure3d_experimental.txt) SI_Figure6 SIFigure6_0p03K.txt - Energy dependence of neutron scattering intensity at 0.03 K (lambda = 10 A), collected on DCS at NIST. SIFigure6_50K.txt - Energy dependence of neutron scattering intensity at 50 K (lambda = 10 A), collected on DCS at NIST. SI_Figure7 SIFigure7_GEM_0p5K-25K.txt - intensity at 0.5 K minus intensity at 25 K as function of Q, collected on GEM at ISIS. SIFigure7_DCS_0p5K-50K.txt - intensity at 0.5 K minus intensity at 50 K as function of Q, collected on DCS at NIST (same as Figure2b_0-5K-50K.txt) SIFigure7_DCS_0p2K-50K.txt - intensity at 0.2 K minus intensity at 50 K as function of Q, collected on DCS at NIST SIFigure7_DCS_0p03K-50K.txt - intensity at 0.03 K minus intensity at 50 K as function of Q, collected on DCS at NIST (same as Figure2b_0-03K-50K.txt) SIFigure7_GEM_4K-25K.txt - intensity at 4 K minus intensity at 25 K as function of Q, collected on GEM at ISIS. SIFigure7_GEM_2K-25K.txt - intensity at 2 K minus intensity at 25 K as function of Q, collected on GEM at ISIS. SIFigure7_GEM_0p9K-25K.txt - intensity at 0.9 K minus intensity at 25 K as function of Q, collected on GEM at ISIS. SIFigure7_GEM_0p6K-25K.txt - intensity at 0.6 K minus intensity at 25 K as function of Q, collected on GEM at ISIS. SI_Figure8 SIFigure8_0p35K-0p5K.txt - intensity at 0.35 K minus intensity at 0.5 K as function of Q, collected on DCS at NIST. SIFigure8_0p3K-0p5K.txt - intensity at 0.3 K minus intensity at 0.5 K as function of Q, collected on DCS at NIST. SIFigure8_0p2K-0p5K.txt - intensity at 0.2 K minus intensity at 0.5 K as function of Q, collected on DCS at NIST. SIFigure8_0p1K-0p5K.txt - intensity at 0.1 K minus intensity at 0.5 K as function of Q, collected on DCS at NIST. SIFigure8_0p03K-0p5K.txt - intensity at 0.03 K minus intensity at 0.5 K as function of Q, collected on DCS at NIST. SI_Figure9 SIFigure9_DCS_0p03K-50K.txt - intensity at 0.03 K minus intensity at 50 K as function of Q, collected on DCS at NIST (same as Figure2b_0-03K-50K.txt and SIFigure7_DCS_0p03K-50K.txt) SIFigure9_MC_nodisorder.txt - Monte Carlo simulation of neutron intensity at 0.2 K minus high T for 0% disorder. SIFigure9_MC_0p01disorder.txt - Monte Carlo simulation of neutron intensity at 0.2 K minus high T for 1% disorder. SIFigure9_MC_0p02disorder.txt - Monte Carlo simulation of neutron intensity at 0.2 K minus high T for 2% disorder. SIFigure9_MC_0p04disorder.txt - Monte Carlo simulation of neutron intensity at 0.2 K minus high T for 4% disorder. SIFigure9_MC_0p06disorder.txt - Monte Carlo simulation of neutron intensity at 0.2 K minus high T for 6% disorder. SI_Figure10 SIFigure10_50K.txt - Energy dependence of neutron scattering at 50 K, lambda = 5 A on DCS, NIST. SIFigure10_0p03K.txt - Energy dependence of neutron scattering at 0.03 K, lambda = 5 A on DCS, NIST. SI_Figure11 SIFigure11_GEM_0p6K-4K.txt - intensity at 0.6 K minus intensity at 4 K as function of Q, collected on GEM at ISIS. SIFigure11_Dy3SbO7magstructure.mcif - magnetic structure for Dy3SbO7.