  An open supersymmetric t-J chain with boundary fields is studied by means of
the Bethe Ansatz. Ground state properties for the case of an almost half-filled
band and a bulk magnetic field are determined. Boundary susceptibilities are
calculated as functions of the boundary fields. The effects of the boundary on
excitations are investigated by constructing the exact boundary S-matrix. From
the analytic structure of the boundary S-matrices one deduces that holons can
form boundary bound states for sufficiently strong boundary fields.
