  We report on the first direct nanoscale imaging of elementary edge
dislocations in a thermotropic chiral smectic C liquid crystal with the Burgers
vector equal to one smectic layer spacing d. We find two different types of
dislocation profiles. In the dislocation of type A, the layers deformations
lack mirror symmetry with respect to the plane perpendicular to the Burgers
vector; the dislocation core size is on the order of d. In the dislocation of
type S, the core is strongly anisotropic, extending along the Burgers vector
over distances much larger (by a factor of 4) than d. The difference is
attributed to a different orientation of the molecular tilt plane with respect
to the dislocation axis; the asymmetric layers distortions are observed when
the molecular tilt plane is perpendicular to the axis and the split S core is
observed when the molecules are tilted along the line.
