Inducing magnetism in the Kondo semiconductor CeRhSb through hydrogenation:: Antiferromagnetic behavior of the new hydride CeRhSbH0.2

CeRhSb was prepared from the elements by arc-melting. A single crystal of this antimonide was investigated on the basis of X-ray diffractometer data: TiNiSi type; Pnma; a = 741.58(9), b = 461.80(9), c = 785.77(8) pm; wR2 = 0.0960; 645 F-2 values; 20 variable parameters. Hydrogenation leads to the formation of the new hydride CeRhSbH0.2 which adopts the same structure but with a slightly larger unit cell volume: a = 742.2(2), b = 462.5(2), c = 787.7(2) pm; wR2 = 0.1444; 443 F-2 values; 20 variable parameters. The rhodium and antimony atoms build up three-dimensional [RhSb] networks with Rh-Sb distances ranging from 268 to 287 pm. The cerium atoms fill distorted hexagonal channels within these networks with one short Ce-Rh contact (310 pm in CeRhSb and 311 pm in CeRhSbH0.2). Susceptibility and specific heat measurements on CeRhSbH0.2 reveal antiferromagnetic ordering at T-N = 3.6(2) K. The experimental magnetic moment in the paramagnetic region is 2.68(5) mu(B)/Ce atom. Magnetization measurements below T-N reveal a spin-flip transition in the range 1.6-2.4 T. Resistivity data show metallic behavior and the characteristics of a Kondo system. Thermoelectric power measurements show a distinct maximum around 106 K with a value of 24 mu V/K. Sb-121 Mossbauer spectroscopic data for CeRhSb and CeRhSbH0.2 at 78 K show only one antimony site. The isomer shift is slightly smaller for the hydrogenated sample indicating a slightly higher electron density at the antimony nuclei of CeRhSbH0.2.