TERNARY ARSENIDES ACUAS(2) AND TERNARY ANTIMONIDES AAGSB(2) (A=RARE-EARTH ELEMENTS AND URANIUM) WITH HFCUSI2-TYPE STRUCTURE

The arsenides ACuAs(2) (A = Y, La-Nd, Sm, Gd-Lu) and the isotypic anti monides AAgSb(2) (A = Y, La-Nd, Sm, Gd-Tm, U) were prepared for the fi rst time and their lattice constants are reported. Single crystals of CeAgSb2 were obtained from a NaCl/KCl flux and their structure was det ermined from four-circle diffractometer X-ray data: P4/nmm, a = 436.3( 1) pm, c = 1069.9(4) pm, Z = 2, R = 0.017 for 381 structure factors an d 12 variable parameters. CeAgSb2 is isotypic with HfCuSi2, CaMnBi2, a nd ZrCuSiAs. In contrast to other ternary lanthanoid transition metal antimonides with HfCuSi2-type structure, the silver site is fully occu pied. Chemical bonding in CeAgSb, can be rationalized by the formula C e3+Ag+Sb-Sb3-, where the superscripts indicate oxidation numbers. (C) 1995 Academic Press, Inc.