  Topological crystalline metals/semimetals (TCMs) have stimulated a great
research interest, which broaden the classification of topological phases and
provide a valuable platform to explore topological superconductivity. Here, we
report the discovery of superconductivity and topological features in
Pb-intercalated transition-metal dichalcogenide Pb$_{1/3}$TaS$_2$. Systematic
measurements indicate that Pb$_{1/3}$TaS$_2$ is a quasi-two-dimensional (q-2D)
type-II superconductor ({\em T}$_c \approx$ 2.8 K) with a significantly
enhanced anisotropy of upper critical field ($\gamma_{H_{c2}}$ =
$H_{c2}^{ab}/H_{c2}^{c}$ $\approx$ 17). In addition, first-principles
calculations reveal that Pb$_{1/3}$TaS$_2$ hosts multiple topological Dirac
fermions in the electronic band structure. We discover four groups of Dirac
nodal lines on the $k_z = \pi$ plane and two sets of Dirac points on the
rotation/screw axes, which are protected by crystalline symmetries and robust
against spin-orbit coupling (SOC). Dirac-cone-like surface states emerge on the
(001) surface because of band inversion. Our work shows that the TCM candidate
Pb$_{1/3}$TaS$_2$ is a promising arena to study the interplay between
superconductivity and topological Dirac fermions.
