Electrical Properties ofTa2H

Data have been obtained on the electrical resistivity, Hall effect, and thermoelectric power in ${\mathrm{Ta}}_2$H from low temperatures to above the hydrogen sublattice order-disorder transformation temperatures. Prominent manifestations of the ${\beta }_1-{\beta }_2$ and ${\beta }_2-\alpha$ transformations are evident in the data, but no clear evidence was found for a splitting of the upper transition such as that reported in the calorimetric studies of Saba et al. Several features of the electrical properties are consistent with the existence of similar conduction-electron dispersions in ${\mathrm{Ta}}_2$H and Ta metal, but other factors appear to be inconsistent with this possibility. Hysteresis was observed in the electrical resistivity in the vicinity of the order-disorder transformations, and possible origins of this hysteresis are discussed. The Hall-effect data show that the majority charge carriers in ${\mathrm{Ta}}_2$H are holes.