  Topological superconductivity with Majorana bound states, which are critical
to implement nonabelian quantum computation, may be realized in
three-dimensional semimetals with nontrivial topological feature, when
superconducting transition occurs in the bulk. Here, we report pressure-induced
superconductivity in a transition-metal dipnictide NbAs2. The emergence of
superconductivity is not accompanied by any structural phase transition up to
the maximum experimental pressure of 29.8 GPa, as supported by
pressure-dependent synchrotron X-ray diffraction and Raman spectroscopy.
Intriguingly, the Raman study reveals rapid phonon mode hardening and
broadening above 10 GPa, in coincident with the superconducting transition.
Using first principle calculations, we determine Fermi surface change induced
by pressure, which steadily increases the density of states without breaking
the electron-hole compensation. Noticeably, the main hole pocket of NbAs2
encloses one time-reversal-invariant momenta of the monoclinic lattice,
suggesting NbAs2 as a candidate of topological superconductors.
