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

We explore bulk superconducting phase in single crystals of the Dirac material LaCuSb₂ 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 LaCuSb₂, and highlights the role of Dirac fermions on its anisotropic character.