  The Lagrangian density of Relativistic Hadrodynamics (RHD) is extended by
introducing non-linear derivative (NLD) interactions of the nucleon with the
meson fields. As a consequence, the nucleon selfenergy becomes both momentum
and density dependent. With a single cut-off parameter, which regulates the NLD
Lagrangian, our approach is compatible with results from microscopic nuclear
matter calculations as well as with Dirac phenomenology. It also reproduces the
correct behavior of the real part of the proton-nucleus potential both at low
and at high proton energies.
