Hydrogenation and physical properties of the ternary germanide CeCoGe: an anisotropic expansion of the unit cell

The ternary germanide CeCoGe and its hydride CeCoGeH crystallize in the tetragonal CeFeSi-type structure but the hydrogenation induces an anisotropic expansion of the unit cell parameters: a decreases (−3.1%) whereas c increases (+12.7%). These structural changes suggest that the hydrogen atoms occupy the [Ce4] tetrahedral sites empty in CeCoGe. Magnetization and electrical resistivity measurements evidence an interesting transition from antiferromagnetic ordering [CeCoGe; TN=5.0(2) K] to spin fluctuation behaviour [CeCoGeH; Tsf=13.3(5) K].