  Whereas SnTe is a inverted band gap topological crystalline insulator, the
topological phase of the alloy Sn_{1-x}In_xTe, a topological superconductor
candidate, has not been clearly studied so far. Our calculations show that the
Sn_{1-x}In_xTe band gap reduces by increasing the In content, becoming a metal
for x>0.1. However, the band inversion at the fcc L point for both gapped and
gapless phases has been maintained. Furthermore, the computed topological
invariant shows a non-trivial phase with a mirror Chern number n_M = -2 for In
concentrations of x=0.03125, x=0.125, and x=0.25. We also identify pairs of
topologically protected states on the (001) surface of Sn_{1-x}In_xTe with +/-
i mirror eigenvalues. The character of these topological states is affected by
In dopant. As the In content x increases, the Dirac crossing point moves
further away from the L point, and the Fermi velocity of the topological states
increases significantly. Our results demonstrate a non-trivial topological
phase for the superconductor Sn_{1-x}In_xTe, and provide a detailed description
of the topological state properties.
