The layered, noncentrosymmetric heavy element ${\text{PbTaSe}}_2$ is found to be superconducting. We report its electronic properties accompanied by electronic-structure calculations. Specific heat, electrical resistivity, and magnetic-susceptibility measurements indicate that PbTaSe${}_2$ is a moderately coupled, type-II BCS superconductor ($T_c=3.72$ K, Ginzburg–Landau parameter $\kappa =17$) with an electron-phonon coupling constant of ${\lambda }_{ep}=0.74$. Electronic-structure calculations reveal a single bulk three-dimensional Dirac cone at the $K$ point of the Brillouin zone derived exclusively from its hexagonal Pb layer; it is similar to the feature found in graphene except there is a 0.8 eV gap opened by spin-orbit coupling. The combination of large spin-orbit coupling and lack of inversion symmetry also results in large Rashba splitting on the order of tenths of an eV.

• Received 30 October 2013
• Revised 27 December 2013

DOI:https://doi.org/10.1103/PhysRevB.89.020505