  We report a high-pressure single-crystal study of the non-centrosymmetric
superconductor YPtBi ($T_c = 0.77$ K). Magnetotransport measurements show a
weak metallic behavior with a carrier concentration $n \simeq 2.2 \times
10^{19}$ cm$^{-3}$. Resistivity measurements up to $p = 2.51$ GPa reveal
superconductivity is promoted by pressure. The reduced upper critical field
$B_{c2}(T)$ curves collapse onto a single curve, with values that exceed the
model values for spin-singlet superconductivity. The $B_{c2}$ data point to an
odd-parity component in the superconducting order parameter, in accordance with
predictions for non-centrosymmetric superconductors.
