Type I and type II superconductivity in a quasi-2D Dirac metal

Dirac material LaCuSb 2 shows anisotropic superconducting response to applied magnetic fields. We explore bulk superconducting phase in single crystals of the Dirac material LaCuSb 2 prepared by the self-flux method. Magnetization, muon spin relaxation measurements, and density functional theory, show the Dirac nodal line Fermi surfaces give rise to type-II superconductivity for magnetic fields applied along the a -axis, and type-I superconductivity for fields along the c -axis. Both chemical and hydrostatic pressure drastically suppress the superconducting transition. We find multiband superconductivity evidenced by a precipitous drop in the electronic specific heat capacity and high-pressure susceptibility for T * < T c /3. Our work demonstrates dirty-limit, weak-coupling multiband superconductivity in LaCuSb 2 , and highlights the role of Dirac fermions on its anisotropic character.