摘要：The Matthias rule, which is an empirical correlation between the superconducting transition temperature ( T c) and the average number of valence electrons per atom ( n ) in alloys and intermetallic compounds, has been used in the past as a guiding principle to search for new superconductors with higher T c. The intermetallic compound SrBi3 (AuCu3 structure) exhibits a T c of 5.6 K. An ab-initio electronic band structure calculation for SrBi3 predicted that T c increases on decreasing the Fermi energy, i.e., on decreasing n , because of a steep increase in the density of states. In this study, we demonstrated that high-pressure (~ 3 GPa) and low-temperature ( n , the T c of (Sr,Na)Bi3 increases to 9.0 K. A new high- T c peak is observed in the oscillatory dependence of T c on n in compounds with the AuCu3 structure. We have shown that the oscillatory dependence of T c is in good agreement with the band structure calculation. Our experiments reaffirm the importance of controlling the number of electrons in intermetallic compounds.
