CRYSTAL-STRUCTURE AND PHYSICAL-PROPERTIES OF BETA-USE2 AND USE2-XTEX (X=0.24 AND 0.72)

The uranium diselenide beta USe2 and the seleno-telluride USe1.76Te0.2 4 crystallize in the orthorhombic system, with the PbCl2 type, space g roup Pnma, and lattice constants a = 7.455(2), b = 4.2320(5), c = 8.96 4(2) Angstrom for beta USe2 and a 7.542(1), b = 4.2491(4), c = 9.006(2 ) Angstrom for USe1.76Te0.24. Their crystal structures were refined fr om single crystal X-ray diffraction data, with conventional R factors 0.064 and 0.046, respectively. Both compounds exhibit ferromagnetism w ith Curie temperatures of 14 K for the former and 33 K for the latter. The structural, electrical, and magnetic properties of these chalcoge nides as well as of beta US2, UTe2 and other mixed chalcogenides are d iscussed. (C) 1996 Academic Press, Inc.