Nematic Superconductivity in Nodal Line Semimetal SnTaS2

Nematic superconductivity spontaneously breaks the rotational symmetry and can host unconventional superconducting phases. Here, we report evidence of intrinsic nematic superconductivity in the nodal-line semimetal SnTaS2, a centrosymmetric layered material with hexagonal symmetry. Transport measurements on exfoliated nanoflakes reveal pronounced twofold in-plane anisotropy in the upper critical field, resistance, and critical current, in contrast to the sixfold lattice symmetry. The anisotropy strength increases with decreasing sample thickness, pointing to a surface-dominated origin, while the variation of the nematic orientation among different devices suggests that the nematic director is weakly pinned. Tunneling spectroscopy on SnTaS2-AlOx-Au junctions further shows a twofold angular modulation of the superconducting gap under in-plane magnetic fields. These results support an unconventional nematic superconducting state associated with the topological surface states and distinct from bulk pairing, establishing SnTaS2 as a promising platform for studying the interplay between the band topology and symmetry-broken superconductivity.