Discovery of topological nodal-line fermionic phase in a magnetic material GdSbTe*

Topological semimetals with accidental band touching between conduction and valence bands protected by time-reversal (TR) and inversion symmetry are at the frontier of modern condensed matter research. Mostly, the discovered topological semimetals are non-magnetic and preserve TR symmetry. Here, we report the systematic electronic structure study of the antiferromagnetic GdSbTe using angle-resolved photoemission spectroscopy (ARPES) as well as first-principles calculations. Our study reveals the presence of nodal-line semimetallic state along the Γ-M direction of the Brillouin zone (BZ). Our data also reveal a robust Dirac like state at X point of the BZ both below and above the magnetic transition temperature (T_N = 13K). With a relatively high transition temperature, GdSbTe can prove to be an archetypical platform to study the interaction between magnetism and topological states of matter.