The La2Sb type silicides and germanides REScSi and REScGe (RE = La, Ce) were synthesized from the elements by arc-melting and subsequent annealing at 1170 K. The structures of LaScSi and LaScGe were refined on the basis of single-crystal X-ray diffraction data. The structures consist of a stacking of two-dimensional [ScSi] networks with ScSi4/4 rectangles, which are separated by rare earth atoms, which leave RE4/4 tetrahedral voids. The latter can be completely filled by hydrogenation leading to the quaternary hydrides REScSiH and REScGeH (RE = La, Ce). Hydrogenation is accompanied by an anisotropic unit cell expansion, i.e., a decrease in the a lattice parameter and a strong increase in c. The H-insertion into the compounds based on cerium induces for both a quasi-2D structure, a strong decrease of their antiferromagnetic ordering; for instance T N decreases from 26 to 3.0 K in the sequence CeScSi → CeScSiH and the occurrence of the influence of the Kondo effect evidenced by electrical resistivity and specific heat measurements. The electronic structure calculation applied to CeScSi and its hydride reveals strong Ce−H bonding influencing the magnetic properties of CeScSiH.

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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 CeRhSbH 0.2 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 CeRhSbH 0.2 ). Susceptibility and specific heat measurements on CeRhSbH 0.2 reveal antiferromagnetic ordering at T N ) 3.6(2) K. The experimental magnetic moment in the paramagnetic region is 2.68(5) µ 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 µV/K. 121 Sb Mössbauer spectroscopic data for CeRhSb and CeRhSbH 0.2 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 CeRhSbH 0.2 .