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

The two intermetallic compounds La4Co2Sn5 and Ce4Co2Sn4 have been synthesized. Both crystallize in the new structure type La4Co2Sn5. From single-crystal analysis they revealed monoclinic symmetry, with space group I2/m, Z=2. The lattice parameters, as obtained from Guinier powder patterns, are a=11.072(2) A, b=4.608(1) A, c=11.375(2) A, β=100.93(1) circle and a=10.983(2) A, b=4.561(1) A, c=11.314(2) A, β=101.02(1) circle, respectively. Resistivity, magnetic and heat capacity measurements show that cerium ions order magnetically with a Neel temperature of 4 K in Ce4Co2Sn5. A ferromagnetic component in the isothermal magnetisation is found in both Ce4Co2Sn5 and La4Co2Sn5 even at 300 K, which can be either intrinsic to these compounds or arise from a trace impurity phase. (orig.)