  Dirac nodal-line semimetals with the linear bands crossing along a line or
loop, represent a new topological state of matter. Here, by carrying out
magnetotransport measurements and performing first-principle calculations, we
demonstrate that such a state has been realized in high-quality single crystals
of SrAs3. We obtain the nontrivial pi Berry phase by analysing the Shubnikov-de
Haas quantum oscillations. We also observe a robust negative longitudinal
magnetoresistance induced by the chiral anomaly. Accompanying first-principles
calculations identify that a single hole pocket enclosing the loop nodes is
responsible for these observations.
