Magnetic phase transitions in UNi2Si2

We report neutron diffraction measurements on a single crystal of UNi2 Si2. Three magnetically ordering phases are observed below 123 K with the magnetic moment parallel to the c-axis in all three phases. The low temperature (T<53 K) phase is a superposition of a commensurate spin density wave with wave vector q = (0 0 0.667±0.002) and a ferromagnetic ordered moment of 1.1±0.3μB, the intermediate (53 K