Specific Heat of Niobium-Tin

The specific heat of Nb₃Sn has been measured over the temperature range 1-42^, and in magnetic fields up to 52. 5 kG. The data can be interpreted to give =13. 1 mJ/g atom ^K^2, {T₂}=2. 4, H₀=5350 G, and (T₂) =21. 7. The Debye temperature appears to increase at the rate of 1^/^ over most of the range of the measurements, with (0) =228^K. Measurements have also been made on a sample of composition Nb₄Sn, and on vapor-grown Nb₃Sn similar to that exhibiting the cubic-tetragonal lattice transformation. The specific heat of Nb₃Sn can be reconciled with elastic-constant data only if it is assumed that the lattice softening implied by the decreasing velocity of sound with decreasing temperatures is limited to frequencies considerably below the Debye frequency.