Rich nature of the topological semimetal states in InBi

Spin-orbit coupling (SOC) plays a significant role in the development of topological physics. For example, considering the SOC effect would lead to the formation of a topological insulator with band inversion in a timereversal symmetry-preserved system and the realization of a Chern phase in a time-reversal symmetry-broken system. Here, by using angle-resolved photoemission spectroscopy combined with first-principles electronic structure calculations, we report SOC-induced "hidden" Dirac bands near the Fermi level in the nonsymmorphic topological semimetal InBi. We clearly observe Dirac-like bulk band crossings located at the corner and boundary of the Brillouin zone, providing compelling evidence for three-dimensional Dirac semimetal states. By means of in situ potassium dosing on the crystal surface, we are able to reveal a partial Dirac nodal line along the kz direction formed by Dirac fermions close to the Fermi level. Our results not only demonstrate the rich topological states in InBi but also offer a good platform for engineering topologically nontrivial phases.