  The nodal line semimetals have attracted much attention due to their unique
topological electronic structure and exotic physical properties. A genuine
nodal line semimetal is qualified by the presence of Dirac nodes along a line
in the momentum space that are protected against the spin-orbit coupling. In
addition, it requires that the Dirac points lie close to the Fermi level
allowing to dictate the macroscopic physical properties. Although the material
realization of nodal line semimetals have been theoretically predicted in
numerous compounds, only a few of them have been experimentally verified and
the realization of a genuine nodal line semimetal is particularly rare. Here we
report the realization of a genuine nodal line semimetal in LaSbTe. We
investigated the electronic structure of LaSbTe by band structure calculations
and angle-resolved photoemission (ARPES) measurements. Taking spin-orbit
coupling into account, our band structure calculations predict that a nodal
line is formed in the boundary surface of the Brillouin zone which is robust
and lies close to the Fermi level. The Dirac nodes along the X-R line in
momentum space are directly observed in our ARPES measurements and the energies
of these Dirac nodes are all close to the Fermi level. These results constitute
clear evidence that LaSbTe is a genuine nodal line semimetal,providing a new
platform to explore for novel phenomena and possible applications associated
with the nodal line semimetals.
