  We introduce momentum-dependent scalar and vector fields into the Lorentz
covariant relativistic BUU- (RBUU-) approach employing a polynomial ansatz for
the relativistic nucleon-nucleon interaction. The momentum-dependent
parametrizations are shown to be valid up to about 1 GeV/u for the empirical
proton-nucleus optical potential. We perform numerical simulations for
heavy-ion collisions within the RBUU-approach adopting momentum-dependent and
momentum-independent mean-fields and calculate the transverse flow in and
perpendicular to the reaction plane, the directivity distribution as well as
subthreshold K+-production. By means of these observables we discuss the
particular role of the momentum-dependent forces and their implications on the
nuclear equation of state. We find that only a momentum-dependent parameter-set
can explain the experimental data on the transverse flow in the reaction plane
from 150 - 1000 MeV/u and the differential K+-production cross sections at 1
GeV/u at the same time.
