Temperature-Dependent Electronic Transition in Cerium Hydride

Resistivity measurements of single crystals of cerium hydride as a function of temperature revealed resistivity anomalies at about 250^∘{}K, which may be associated with a previously reported compositional metal-to-semiconductor transition. Precise x-ray diffractiometry disclosed that the cubic fluorite type structure of cerium hydride becomes slightly tetragonal below 250^∘{}K. Neutron-diffraction investigations showed no apparent ordering of excess hydrogen atoms in octahedral interstices and magnetic-susceptibility measurements showed no magnetic ordering. Results of thermoelectric-power measurements are in agreement with a model involving the formation of a defect band to explain the metallic behavior of cerium hydride.