THE CRYSTAL-STRUCTURE OF THE NOVEL TERNARY SILICIDE SM4PD4SI3

The crystal structure of the compound Sm4Pd4Si3 was determined by the single-crystal method (KM-4 automatic diffractometer, Mo K alpha radia tion). Sm4Pd4Si3 has the monoclinic Nd4Rh4Ge3 type structure: space gr oup C2/c, mC44 (No. 15), a = 20.693(6), b = 5.584(1), c = 7.699(2) Ang strom, beta = 109.48(3)degrees, V = 838 Angstrom(3), Z = 4, mu = 36.23 mm(-1), R(F) = 0.0537, R(w) = 0.0435 for 1652 unique reflections. The coordination numbers of samarium atoms are 17 and 18. For palladium a nd silicon atoms icosahedra and trigonal prisms with additional atoms are typical as coordination polyhedra. The structure of Sm4Pd4Si3 is c omposed of fragments of the YPd2Si and Y3Rh2Si2 structure in a ratio 1 :1.