${\mathrm{Re}}_6\mathrm{Hf}$, which crystallizes in $\alpha$-Mn structure(space group $I\overline{4}3m)$ without a spatial inversion center, is a superconductor with a superconducting transition temperature $T_c\approx 6.2\mathrm{K}$. The measurements of magnetic susceptibility $\left(\chi \right)$, resistivity $\left(\rho \right)$, and specific heat capacity $\left(C\right)$ were carried out. Bulk superconductivity is revealed by the jump at $T_c$ of the specific heat with $\mathrm{\Delta }C/{\gamma }_n{T}_c\approx 1.63$, suggesting moderate electron-electron coupling strength in this system. The upper critical field ${\mu }_0{H}_{c2}^{WHH}\left(0\right)$ was estimated to be of 89 kOe, and ${\mu }_0{H}_{c2}^{GL}\left(0\right)=107$ kOe, which is close to the Pauli limiting field. The Ginzburg Landau parameter ${\kappa }_{GL}=50.2$, indicates that ${\mathrm{Re}}_6\mathrm{Hf}$ is a type-II superconductor. The temperature dependence of the electronic specific heat $C_{el}\left(T\right)$ in the superconducting state can be explained by BCS theory. Furthermore, the magnetic-field dependence of $\gamma \left(H\right)$ is found to be linear with respect to $H$. These results imply a dominant $s$-wave superconductivity in ${\mathrm{Re}}_6\mathrm{Hf}$.

• Received 18 April 2016

DOI:https://doi.org/10.1103/PhysRevB.94.024518