  We investigate nuclear matter properties in the relativistic Brueckner
approach. The in-medium on-shell T-matrix is represented covariantly by five
Lorentz invariant amplitudes from which we deduce directly the nucleon
self-energy. To enforce correct Hartree-Fock results we develop a subtraction
scheme which treats the bare nucleon-nucleon potential exactly in accordance to
the different types of meson exchanges. For the higher order correlations we
employ two different covariant representations in order to study the
uncertainty inherent in the approach. The nuclear matter bulk properties are
only slightly sensitive on the explicit representation used. However, we obtain
new Coester lines for the various Bonn potentials which are shifted towards the
empirical region of saturation.
