  The electronic structure of Sb(110) is studied by angle-resolved
photoemission spectroscopy and first-principle calculations, revealing several
electronic surface states in the projected bulk band gaps around the Fermi
energy. The dispersion of the states can be interpreted in terms of a strong
spin-orbit splitting. The bulk band structure of Sb has the characteristics of
a strong topological insulator with a Z2 invariant nu0=1. This puts constraints
on the existence of metallic surface states and the expected topology of the
surface Fermi contour. However, bulk Sb is a semimetal, not an insulator and
these constraints are therefore partly relaxed. This relation of bulk topology
and expected surface state dispersion for semimetals is discussed.
