  The large single crystals of SrSnP were prepared using Sn self-flux method.
The superconductivity in the tetragonal SrSnP is observed with the critical
temperature of ~2.3 K. The results of a crystallographic analysis,
superconducting characterization, and theoretical assessment of tetragonal
SrSnP are presented. The SrSnP crystallizes in the CaGaN structure type with
space group P4/nmm (S.G.129, Pearson symbol tP6) according to the single
crystal X-ray diffraction characterization. A combination of magnetic
susceptibility, resistivity, and heat capacity measurements confirms the bulk
superconductivity with Tc = 2.3(1) K in SrSnP. According to the X-ray
photoelectron spectroscopy (XPS) measurement, the assignments of Sr2+ and P3-
are consistent with the chemical valence electron balance principles. Moreover,
it is highly likely that Sn atom has only one unusual oxidation state.
First-principles calculations indicate the bands around Fermi level are
hybridized among Sr-d, Sn-p, and P-p orbitals. The strong Sn-P and Sr-P
interactions pose as keys to stabilize the crystallographic structure and
induce the superconductivity, respectively. The physics-based electronic and
phononic calculations are consistent with the molecular viewpoint. After
including the spin-orbit coupling (SOC) into the calculation, the band
degeneracies at gamma-point in the first Brillouin zone (BZ) split into two
bands, which yield to the van Hove singularities around Fermi level.
