Synthesis, crystal structure, magnetic and transport properties of the newintermetallic compounds R4Co2Sn5 (R=La, Ce)

The two intermetallic compounds La4Co2Sn5 and Ce4Co2Sn5 have been synthesiz ed. Both crystallize in the new structure type La4Co2Sn5. From single-cryst al analysis they revealed monoclinic symmetry, with space group 12/m, Z = 2 . The lattice parameters, as obtained from Guinier powder patterns, are a = 11.072(2) Angstrom, b = 4.608(1) Angstrom, c = 11.375(2) Angstrom, beta = 100.93(1)degrees and a = 10.983(2) Angstrom, b = 4.561(1) Angstrom, c = 11. 314(2) Angstrom, beta = 101.02(1)degrees, respectively. Resistivity, magnet ic and heat capacity measurements show that cerium ions order magnetically with a Neel temperature of 4 K in Ce4Co2Sn5. A ferromagnetic component in t he isothermal magnetisation is found in both Ce4Co2Sn5 and La4Co2Sn5 even a t 300 K, which can be either intrinsic to these compounds or arise from a t race impurity phase. (C) 2000 Elsevier Science S.A. All rights reserved.