THE CRYSTAL-STRUCTURE OF NDFE1-XSB2 AND ISOTYPIC COMPOUNDS RE(FE,CO)1-XSB2, RE=LA, CE, PR, SM AND GD

New compounds REFe1-xSb2 and RECO1-xSb2, RE = La, Ce, Pr, Nd, Sm and G d, have been synthesized by argon arc melting elemental mixtures follo wed by annealing at 800-degrees-C for 7 days. The crystal structure of NdFe1-xSb2 has been determined from single-crystal X-ray counter data . NdFe1-xSb2 crystallizes in the ZrCuSi2 structure type with the centr osymmetric space group P4/nmm. The tetragonal lattice parameters are a =0.43514(6) nm and c = 0.96518(13) nm; Z = 2. For 273 reflections (\F( o)\ > 2sigma) the residual values are R(F) = SIGMA\DELTAF\/SIGMA\F(o)\ = 0.0532 and R(w) = 0.0516. Compounds with the light rare earth eleme nts La, Ce, Pr, Sm and Gd were found to be isotypic with NdFe1-xSb2.