  We grew single-crystal thin films of a topological crystalline insulator
(TCI) SnTe with a smooth surface at the atomic scale by molecular beam epitaxy
(MBE). In the magnetoresistance (MR) measurement, we observed both positive and
negative components near zero magnetic field at lowest temperatures of 2 - 3 K,
while we observed only a negative MR at elevated temperatures of 6 - 10 K. The
positive MR is attributed to the weak antilocalization (WAL) in the transport
through the topological surface state (SS), demonstrating $\pi$ berry phase
which is essential to the topological SS, while the negative MR to the weak
localization (WL) in the transport through the bulk state (two-dimensional bulk
subbbands). The absolute value of the prefactor $ \alpha $ deduced from the
fitting of the observed positive MR to the Hikami-Larkin-Nagaoka equation was
much smaller than expected from the number of transport channel of the SS,
suggesting the coupling of the SS to the bulk state.
