Electron-electron interaction and normal-state transport in superconducting Ti-(Sn, Ge) alloys

We have measured the resistivity as a function of temperature, ρ(T), of superconducting (Formula presented)(Sn, Ge(Formula presented) (0.03 ≲x≲ 0.12 for Ti-Sn and 0.03 ≲x≲ 0.07 for Ti-Ge) alloys below 25 K. These alloys are chosen because, upon dilute alloying, their impurity resistivities (Formula presented) vary readily from ≊55 to ≊150 μΩ cm, while their superconducting transition temperatures (Formula presented) increase moderately by a factor ∼60%. We find that the overall behavior of ρ(T) can be quantitatively interpreted in terms of the Boltzmann transport (Formula presented) (with A being a constant and n an exponent) plus a temperature-dependent contribution Δ(Formula presented) arising from electron-electron interaction effects in the presence of disorder. Particularly, we observe a disorder dependence of Δ(Formula presented)∼(Formula presented). We also observe that the screened Coulomb interaction parameter F̃, defined in the electron-electron interaction theory, becomes much more negative in samples with increasing (Formula presented).