A case for Bragg diffraction by a noncollinear (PT)-symmetric antiferromagnet Cu$_2$(MoO$_4$)(SeO$_3$)

Antiferromagnetic compounds chromium sesquioxide (Cr$_2$O$_3$) and dioxomolybdenum selenite present linear magnetoelectric effects. Anti-inversion symmetry in the corresponding magnetic crystal classes dictate the makeup of magnetic Bragg diffraction patterns. Copper axial and polar magnetic multipoles contribute to resonant x-ray and magnetic neutron amplitudes in a symmetry informed analysis of monoclinic Cu$_2$(MoO$_4$)(SeO$_3$) presented with a view to steering future diffraction experiments. The compound might be viewed as a low-dimensional quantum magnet on account of its crystal structure and extreme Cu spin (S = 1/2).