Hydrogenation of the ternary silicides RENiSi (REÂ =Â Ce, Nd) crystallizing in the tetragonal LaPtSi-type structure

Hydrogenation of isostructural RENiSi (RE = Ce, Nd) intermetallic compounds has been performed. Neutron diffraction experiments on CeNiSiD1.2(1) indicates that D-atoms fully occupy the [Ce3Ni2]- and partially fill the [Ce3Si2]-bipyramidal sites. The strong hybridisation between Ce and D in these sites can explain the observed increase of the cerium valence after deuterium insertion. The magnetic phase diagram of NdNiSi has been established and highlights two antiferromagnetic transitions at TN1 = 6.8(2) K and TN2 = 2.8(2) K, which disappear after hydrogenation.