Strong-Coupling Calculation of the Upper Critical Field of Amorphous Lead

A calculation of the upper critical field Bc2(T) is presented for the amorphous superconductor Pb0.75{Bi}0.25$. Experimentally measured ${{α}}²F({Ω})$ and ${{μ}}*$ are used in the strong-coupling theory for ${B}c2(T)$. We show that the anomalous behavior of ${B}c2(T)$ at low temperatures, which has been found recently, can be explained quantitatively by the influence of the anomalously enhanced low-frequency part in ${{α}}²F({Ω})$. In addition, spin-polarization effects are considered and it is shown that due to strong-coupling effects their contribution is unimportant for ${Pb}0.75Bi0.25.