  We continue the study of the $u(2|2)$-supersymmetric extension of the Hubbard
model in one dimension. We determine the excitation spectrum at zero
temperature even in the sectors where the ground states are
$u(2|2)$-descendants of Bethe states. The excitations include spinons, holons,
electrons, localons (local electrons pairs, moving coherently through the
lattice) and their bound states. The spectra are found to be very different for
repulsive and attractive on-site interaction. We also study the thermodynamics
of the model.
