  The discovery of signatures of topological superconductivity in
superconducting bulk materials with topological surface states has attracted
intensive research interests recently. Utilizing angle-resolved photoemission
spectroscopy and first-principles calculations, here, we demonstrate the
existence of topological nodal-line states and drumheadlike surface states in
centrosymmetric superconductor SnTaS2, which is a type-II superconductor with a
critical transition temperature of about 3 K. The valence bands from Ta 5d
orbitals and the conduction bands from Sn 5p orbitals cross each other, forming
two nodal lines in the vicinity of the Fermi energy without the inclusion of
spin-orbit coupling (SOC), protected by the spatial-inversion symmetry and
time-reversal symmetry. The nodal lines are gapped out by SOC. The drumheadlike
surface states, the typical characteristics in nodal-line semimetals, are quite
visible near the Fermi level. Our findings indicate that SnTaS2 offers a
promising platform for exploring the exotic properties of the topological
nodal-line fermions and gives a help to study topological superconductivity.
