Quantum oscillations and anisotropic magnetoresistance in a quasi-two-dimensional Dirac nodal line superconductor

Quantum materials that exhibit both superconductivity and non-trivial band topology have garnered significant interest recently, as band topology may lead to topological or unconventional superconductivity. To date, the superconductivity in most topological materials is found to be type-II. However, the band topology of topological semimetals with type-I superconductivity has been less explored. Here, we identify a quasi-two-dimensional non-magnetic Yb-based compound as such a candidate, which is a type-I superconductor below 1.3 K. We show that it has a Dirac nodal line in the normal state according to our ab-initio density functional theory (DFT) calculations. We provide evidence for the Dirac nodal line through quantum oscillation measurements. Furthermore, we observe non-monotonic angle dependence of the quantum oscillation and magnetoresistance, not typically observed in two-dimensional materials. Such phenomena can be explained by the specific Fermi surface geometry, as reflected in our DFT analysis. Our work presents this quasi-2D Yb compound as a possible topological superconductor.