  Topological Dirac semimetals with accidental band touching between conduction
and valence bands protected by time reversal and inversion symmetry are at the
frontier of modern condensed matter research. Theoretically one can get Weyl
and/or nodal-line semimetals by breaking either one of them. Most of the
discovered topological semimetals are nonmagnetic i.e respect time reversal
symmetry. Here we report the experimental observation of a topological
nodal-line semi metallic state in GdSbTe using angle-resolved photoemission
spectroscopy. Our systematic study reveals the detailed electronic structure of
the paramagnetic state of GdSbTe. We observe the presence of multiple Fermi
surface pockets including a diamond-shape, an elliptical shape, and small
circular pockets around the zone center and high symmetry M and X points of the
Brillouin zone (BZ), respectively. Furthermore, we observe the presence of a
Dirac-like state at the X point of the BZ. Interestingly, our experimental data
shows a robust Dirac like state both below and above the magnetic transition
temperature (T_N ~ 13 K). Having relatively higher transition temperature,
GdSbTe provides an archetype platform to study the interaction between
magnetism and topological states of matter.
