Resistive behaviour of PrH_2+x compounds at the approach of the metal—insulator transition

Abstract

Electrical measurements for PrH_2+x compounds with 0≤x≤O•75 show a metallic behaviour below room temperature. There is strong evidence in favour of structural ordering (short range for × < 0•1 and long range for × > 0•2) within the H sublattice for all concentrations x. A qualitative analysis of the phonon resistivity and of the disorder resistivity implies a strong reduction in the carrier density with increasing x; this places this system near to a metal-insulator transition as in CeH_2+x and LaH_2+x. We observe also that the mobility of the H atoms increases with increasing x.