New Hydrides REScSiH and REScGeH (RE = La, Ce): Structure, Magnetism, and Chemical Bonding

Abstract

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 TN 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 spe...