LOW-TEMPERATURE SPECIFIC-HEAT MEASUREMENTS OF VSI2, NBSI2, AND TASI2

The disilicides of vanadium, niobium and tantalum are isoelectronic. They crystallize in the same hexagonal structure (type C40 space group P6(2)22) with lattice parameters increasing by about 4% from the vanadium to the tantalum compound. We report specific heat measurements for the three compounds in the temperature range from 100 mK to 7.5 K. We used a transient heat pulse technique and low temperatures were achieved with a dilution refrigerator. From the results we determined the electronic contribution to the specific heat gamma T as well as the phonon contribution beta T-3. gamma is twice larger for VSi2 than for the other two compounds and the density of states at the Fermi level, D(E(F)), determined from gamma is in rather good agreement with the theoretical calculations of the band structures from the literature. The Debye temperature theta(D) deduced from beta varies as M(-1/2) where M is the molar mass.