  The properties of asymmetric nuclear matter have been investigated in a
relativistic Dirac-Brueckner-Hartree-Fock framework using the Bonn A potential.
The components of the self-energies are extracted by projecting on Lorentz
invariant amplitudes. Furthermore, the optimal representation scheme for the
$T$ matrix, the subtracted $T$ matrix representation, is applied and the
results are compared to those of other representation schemes. Of course, in
the limit of symmetric nuclear matter our results agree with those found in
literature. The binding energy $E_b$ fulfills the quadratic dependence on the
asymmetry parameter and the symmetry energy is 34 MeV at saturation density.
Furthermore, a neutron-proton effective mass splitting of $m_n^* < m_p^*$ is
found. In addition, results are given for the mean-field effective coupling
constants.
