, probed via X-ray resonant exchange scattering*

Intrinsic magnetic topological insulators devoid of defects and disorder which can be detrimental to topological quantum phenomena are of interest. Since magnetism breaks time reversal symmetry and allows to tune the system's spatial symmetry thereby opening a way to induce exotic phenomena such as axion states. In this work, we used high-resolution resonant X-ray scattering to study magnetic long-range order in the recently discovered topological material EuSn₂As₂. In this rhombohedral system an antiferromagnetic (AFM) transition is observed below 25 K. Our diffraction studies revealed a long-range three dimensionally ordered magnetic phase with an ordering vector, q=(0,0,1/2), indicating a 2-unit-cell magnetic periodicity along the c axis in hexagonal notation and consisting of ferromagnetic Eu-layers stacked in an antiferromagnetic fashion. Order parameter data indicates a T_N of 24.1K.