jats:titleAbstract</jats:title> jats:pAxion-like particles (ALPs) can induce localized oscillatory modulations in the spectra of photon sources passing through astrophysical magnetic fields. Ultra-deep jats:italicChandra</jats:italic> observations of the Perseus cluster contain over jats:inline-formula jats:tex-math

</jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjaa8b16ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> counts from the active galactic nucleus (AGN) of the central cluster galaxy NGC1275 and represent a data set of extraordinary quality for ALP searches. We use this data set to search for X-ray spectral irregularities from the AGN. The absence of irregularities at the jats:inline-formula jats:tex-math

</jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjaa8b16ieqn2.gif" xlink:type="simple" /> </jats:inline-formula> level allows us to place leading constraints on the ALP-photon mixing parameter jats:inline-formula jats:tex-math

</jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjaa8b16ieqn3.gif" xlink:type="simple" /> </jats:inline-formula> for jats:inline-formula jats:tex-math

</jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjaa8b16ieqn4.gif" xlink:type="simple" /> </jats:inline-formula>, depending on assumptions on the magnetic field realization along the line of sight.</jats:p>