Nonsymmorphic symmetry-protected band crossings in a square-net metal PtPb4

Abstract Topological semimetals with symmetry-protected band crossings have emerged as a rich landscape to explore intriguing electronic phenomena. Nonsymmorphic symmetries in particular been shown play an important role protecting the along line (rather than point) momentum space. Here we report experimental and theoretical evidence for Dirac nodal Brillouin zone boundaries PtPb 4 , arising from nonsymmorphic symmetry of its crystal structure. Interestingly, while lines would remain gapless absence spin–orbit coupling (SOC), SOC, this case, plays detrimental topology by lifting degeneracy everywhere except at set isolated points. Nevertheless, is observed bandwidth much smaller that found density functional theory (DFT). Our findings reveal be material system narrow approximately protected crystalline symmetries.