Superconducting transition temperature of the equiatomic ZrNb alloy at pressures to 56.4 GPa

The superconducting transition temperature of the equiatomic ZrNb alloy is measured in dependence on pressure to 56.4 GPa. The T_c( P) dependence is found to achieve a maximum around 42 GPa and to have an anomalous behavior with a shallow minimum in the pressure range 5-10 GPa. This behavior of T_c( P) is similar to that earlier observed on pure metal Nb. A comparison with recent model calculations suggests that the features of the T_c( P) behavior both in pure Nb and in the ZrNb alloy are of the same nature and result from the high-pressure anomalies in their phonon spectra.