  The electronic properties relevant to the superconductivity are reported for
bulk Ta-Hf and Ta-Zr body centered cubic alloys, in large part to determine
whether their properties are suitable for potential use in superconducting
qbits. The body centered cubic unit cell sizes increase with increasing
alloying. The results of magnetic susceptibility, electrical resistivity and
heat capacity characterization are reported. While elemental Ta is a type I
superconductor, the alloys are type II strong coupling superconductors.
Although decreasing the electron count per atom is expected to increase the
density of electronic states at the Fermi level and thus the superconducting
transition temperature (Tc) in these systems, we find that this is not
sufficient to explain the significant increases in the superconducting Tc's
observed.
