  Quasiparticle states bound to the boundary of anisotropically paired
superconductors, their contributions to the density of states and to the
conductance of NIS junctions are studied both analytically and numerically. For
smooth surfaces and real order parameter we find some general results for the
bound state energies. In particular, we show that under fairly general
conditions quasiparticle states with nonzero energies exist for momentum
directions within a narrow region around the surface normal. The energy
dispersion of the bound states always has an extremum for the direction along
the normal. Along with the zero-bias anomaly due to midgap states, we find, for
quasi two-dimensional materials, additional low-temperature peaks in the
conductance of NIS junctions for voltages determined by the extrema of the
bound state energies. The influence of interface roughness on the conductance
is investigated within the framework of Ovchinnikov's model. We show that
nonzero-bias peaks at low temperatures may give information on the order
parameter in the bulk, even though it is suppressed at the surface.
