  Orthorhombic (space group: Pnma) Nb2P5 is a high-pressure phase that is
quenchable to ambient pressure, which could viewed as the zigzag infinite P
chain-inserted NbP2. We report herein the high-pressure crystal growth of Nb2P5
and the discovery of its superconducting transition at Tc ~ 2.6 K. The
electrical resistivity, magnetization, and specific heat capacity measurements
on the high-quality crystal unveiled a conventional type-II weakly coupled
s-wave nature of the superconductivity, with the upper critical field Hc2(0) ~
0.5 T, the electron-phonon coupling strength {\lambda}ep ~ 0.5 - 0.8, and the
Ginzburg-Landau parameter \k{appa} ~ 100. The ab initio calculations on the
electronic band structure unveiled nodal-line structures protected by different
symmetries. The one caused by band inversion, for example, on the {\Gamma}-X
and U-R paths of the Brillouin zone, likely could bring nontrivial topology and
hence possible nontrivial surface state on the surface. The surface states on
the (100), (010) and (110) surfaces were also calculated and discussed. The
discovery of the phosphorus-rich Nb2P5 superconductor would be instructive for
the design of more metal phosphides superconductors which might host
unconventional superconductivity or potential technical applications.
