Bulk and surface electronic structure of hexagonal structured PtBi$_{\mathrm{2}}$ studied by angle-resolved photoemission spectroscopy

PtBi$_{\mathrm{2}}$ with a layered hexagonal crystal structure was recently reported to exhibit an unconventional large linear magnetoresistance. Using angle-resolved photoemission spectroscopy, we present a systematic study on its bulk and surface electronic structure. Through comparison with first-principle calculations, our experiment distinguishes the low-lying bulk bands from entangled surface states. We find significant electron doping in PtBi$_{\mathrm{2}}$, implying a substantial Bi deficiency induced disorder therein. Intriguingly, we discover a Dirac-cone-like surface state without topological protection on the boundary of the Brillouin zone. Our findings exclude linear band dispersion in the quantum limit as the cause of the unconventional large linear magnetoresistance but put support to the classical disorder model from the perspective of the electronic structure.