Coexistence of Dirac Nodal Lines and Rashba Bands in the Topological Superconductor Candidate AuSn4.

The interplay between spin-orbit coupling and superconductivity in topologically nontrivial materials provides a fertile setting for realizing unconventional pairing states and Majorana bound modes. AuSn4, a noble metal stannide isostructural to PtSn4 and PdSn4, has recently been identified as a candidate two-dimensional superconductor exhibiting vortex core zero modes consistent with mixed s + p pairing symmetry. Here, we present a comprehensive study using angle-resolved photoemission spectroscopy (ARPES) and spin-resolved ARPES (SARPES), unveiling the coexistence of Rashba-split surface bands and Dirac nodal lines in AuSn4. We further identify a surface-confined van Hove singularity (VHS) in close proximity to the Dirac point near the Brillouin zone boundary. Together, these results position AuSn4 as a compelling superconducting platform within which Rashba type surface states and nontrivial topological bands reside, offering microscopic insight into the emergence of unconventional pairing and the prospects for topological superconductivity.