  We provide an explicit normal distinguished boundary dilation to a pair of
commuting operators $(S,P)$ having the closed symmetrized bidisc $\Gamma$ as a
spectral set. This is called Sz.-Nagy dilation of $(S,P)$. The operator pair
that dilates $(S,P)$ is obtained by an application of Stinespring dilation of
$(S,P)$ given by Agler and Young. We further prove that the dilation is minimal
and the dilation space is no bigger than the dilation space of the minimal
unitary dilation of the contraction $P$. We also describe model space and model
operators for such a pair $(S,P)$.
