  SnTe belongs to the recently discovered class of topological crystalline
insulators. Here we study the formation of line defects which break crystalline
symmetry by strain in thin SnTe films. Strained SnTe(111) films are grown by
molecular beam epitaxy on lattice- and thermal expansion coefficient-mismatched
CdTe. To analyze the structural properties of the SnTe films we applied {\em
in-situ} reflection high energy electron diffraction, x-ray reflectometry, high
resolution x-ray diffraction, reciprocal space mapping, and scanning tunneling
microscopy. This comprehensive analytical approach reveals a twinned structure,
tensile strain, bilayer surface steps and dislocation line defects forming a
highly ordered dislocation network for thick films with local strains up to
31\% breaking the translational crystal symmetry.
