Electronic structure of the dual-topology semimetal Pt2HgSe3

We report high-resolution angle-resolved photoemission measurements on single crystals of Pt2HgSe3 grown by high-pressure synthesis. Our data reveal a gapped Dirac nodal line whose (001) projection separates the surface Brillouin zone in topological and trivial areas. In the nontrivial k-space range, we find surface states with multiple saddle points in the dispersion, resulting in two van Hove singularities in the surface density of states. We identify these surface states as signatures of a topological crystalline state, which coexists with a weak topological phase.