Crystal and magnetic structure in the itinerant 5f antiferromagnet UCr2Si2

We have grown a single crystal of UCr₂Si₂ for the first time. UCr₂Si₂ exhibits a structural transition from the ThCr₂Si₂-type structure (I4/mmm) to the triclinic (Pbar 1) structure below T_a = 210 K. An antiferromagnetic structure was determined by neutron diffraction below T_N = 27 K, with a propagation vector Q = [-1/2, 1/2, 0] and a magnetic moment 0.65 mu_B/U oriented along [0, 0, 1] direction.