Resistivity and Electron-phonon Coupling in Dilute Superconducting Nb-Ta Alloys

Resistive methods have been used to estimate the electron-phonon coupling in superconducting Nb-Ta alloys. It is found that a calculation of the transition temperature from McMillan's formula with normal state quantities and one adjustable parameter is accurate to about 5% over the concentration region up to 20 at% Ta. Conversely, the superconducting transition temperature, the Debye temperature and resistive data confirm qualitatively the existence of a previously observed anomaly in the electronic specific heat coefficient. Different estimates of the electron-phonon coupling constant are discussed.