Single crystal study on UNi0.5Sb2

Single crystals of UNi_1−xSb₂ have been grown from an Sb-rich melt and studied by means of X-ray diffraction, magnetic and electrical transport measurements. Crystal structure refinements indicated significant deficiency on the transition metal sites in the tetragonal HfCuSi₂-type unit cell, yielding the actual composition UNi_0.5Sb₂. The single crystals studied order antiferromagnetically below T_N=161 K and exhibit another phase transition at T_t=60 K, presumably caused by a spin-reorientation. No crystal structure distortion could be detected at 10 K. Above T_N the electrical resistivity is dominated by a Kondo effect, whereas at lower temperatures it shows a behavior characteristic of antiferromagnets. The overall magnetic and electrical transport properties of UNi_0.5Sb₂ are highly anisotropic both in the ordered and paramagnetic states.