Single cry~aals of U2Te3 were obtained by solid state reaction between the elements in stoichiometric proportions mixed with a small quantity of cesium chloride. U2Te3 crystallizes in the orthorhombic system, space group Pnma (n ° 62), with unit cell parameters a = 12.175(2),~, h = 4.370(1)A, c = 11.828(2)A, and Z =4. The structure was determined from single crystal X-ray diffraction data and refined to final residual factors R(F) = 0.030 and Rm(F) = 0.035 for 32 variable parameters and a unique data set of 1100 diffraction intensities [I > 3¢7(I)]. The U atoms are located on two 4¢ non equivalent crystallographic positions. U(I) has a 7-fold coordination of Te atoms with a coordination polyhedron deriving from an octahedron in which one apex is split into two positions, and U(2) has a monocapped trigonal prismatic coordination. U2Te3 exhibits rather complex magnetic behaviour, with an onset of ferromagnetic order at T -110 K and spin reorientation below 105 K.
Intreductton
The crystallo-ehemistry of uranium chalcogeaides has been investigated by many authors in the past years, but some of the reported structure types have not yet been fully characterized from single crystal Xray diffraotion data. The uranium sesquichalcagenides U2X 3 (X = S, Se, Te)