Growth, Crystal Structure, and Thermopower of Single Crystals of UNi1.9Sn

We have grown single crystals of UNi1.9(1)Sn from a semi-levitated melt using the Kyropoulos technique. The crystal structure of UNi1.9(1)Sn was determined by single-crystal X-ray diffraction and refined to a residual value of R=0.0336. This compound crystallizes in the cubic MnCu2Al-type structure with the lattice parameter a=6.4633(4) ?. The temperature dependence of the thermoelectric power, different from that observed for UNi2Sn polycrystalline material, exhibits no anomalies other than a broad peak near 60 K. The present data suggest a high sensitivity of the physical properties of these intermetallics to the presence of vacancies on transition metal sites.