  We report a study of the normal- and superconducting-state electronic
properties of the centrosymmetric compound SrPt3P via 31P
nuclear-magnetic-resonance (NMR) and magnetometry investigations. Essential
features such as a sharp drop of the Knight shift at T < Tc and an exponential
decrease of the NMR spin-lattice relaxation ratio 1/(T1T) below Tc are
consistent with an s-wave electron pairing in SrPt3P, although a direct
confirmation in the form of a Hebel-Slichter-type peak is lacking. Normal-state
NMR data at T < 50 K indicate conventional features of the conduction
electrons, typical of simple metals such as lithium or silver. Our data are
finally compared with available NMR results for the noncentrosymmetric
superconductors LaPt$_3$Si and CePt$_3$Si, which adopt similar crystal
structures.
