  Domain walls can be formed in superconductors with a discrete degeneracy of
the ground state, for instance, due to the breaking of time reversal symmetry.
We study all cases where the formation of domain walls is possible in a
tetragonal superconductor with the point group $D_{4h}$. We discuss both
triplet and mixed singlet order parameters. It is found that in all cases the
domain walls support subgap Andreev bound states, whose energies strongly
depend on the direction of semiclassical propagation. The bound state
contribution to the density of quasiparticle states exhibits peculiar features,
which can be observed in tunneling experiments.
