A series of novel ternary compounds RE(6)Msb(15) has been synthesized (a) via are melting elemental metal ingots (M = Mn or Cu) or (b) via reaction sintering cold compacted powder blends (M = Zn). The crystal structure was solved for La6MnSb15 from single crystal X-ray counter data (La6MnSb15-type, Imm2, Z = 2, a = 1.5376, b = 1.9611, c = 0.4314 nm, R(F) = 0.067 for 923 reflections (\F-0\ > 3 sigma)). The Rietveld refinement of the crystal structure of Ce6MnSb15 using CuK alpha-X-ray data from a D5000 Siemens diffractometer confirmed atom order and crystal symmetry Imm2 (R(I) = 0.049, R(F) = 0.031) and revealed small deficiencies in the Mn site as well as for one of the Sb sites. Employing X-ray powder Guinier techniques the new compounds were all found to be isostructural with the La6MnSb15 type. Magnetic measurements performed down to liquid helium temperature give evidence that both compounds Ce6MnSb15 and Gd6ZnSb15 undergo an antiferromagnetic transition at 7 and 15 K, respectively. Ce6ZnSb15 and Pr6ZnSb15 remain paramagnetic in the temperature range investigated, whereas Sm6ZnSb15 is a Van-Vleck-type paramagnet. (C) 1996 Academic Press, Inc.
