  Rhenium-based superconductors have recently attracted significant interest
due to their unconventional superconducting properties. In this work, we report
the synthesis and properties of new superconducting Re$_{7}$X$_{3}$ (X = Nb,
Ta, Ti, Zr, Hf) binary alloys which maintain a fixed composition of rhenium
while crystallizing in centrosymmetric to non-centrosymmetric crystal
structures, depending on the elements of the X site. Comprehensive structural
and superconducting properties were investigated using powder x-ray
diffraction, AC transport, magnetization, and specific heat measurements, and
on the basis of these measurements, the superconducting phase diagram was
constructed. The results suggest a complex interplay of crystal structure and
the Re/X ratio, which governs the strength of spin-orbital coupling and
controls the unconventional superconducting behavior in Re-based
superconductors.
