  The interplay between topological electronic structure and superconductivity
has attracted tremendous research interests recently as they could induce
topological superconductivity (TSCs) which may be used to realize topological
qubits for quantum computation. Among various TSC candidates, superconducting
BaSn3 (Tc ~ 4.4 K) has been predicted to be a topological Dirac semimetal (TDS)
hosting two pairs of Dirac points along the G - A direction. Here, by combining
the use of angle-resolved photoemission spectroscopy and ab initio
calculations, we identified the predicted topological Dirac fermions and
confirmed the TDS nature of the compound. In addition, we observed surface
states connecting the Dirac points. Our observations demonstrate BaSn3 as a
superconductor with nontrivial topological electronic structures.
