  Azimuthal distributions of charged particles and intermediate mass fragments
emitted in Au+Au collisions at 600AMeV have been measured using the FOPI
facility at GSI-Darmstadt. Data show a strong increase of the in-plane
azimuthal anisotropy ratio with the charge of the detected fragment.
Intermediate mass fragments are found to exhibit a strong momentum-space
alignment with respect of the reaction plane. The experimental results are
presented as a function of the polar center-of-mass angle and over a broad
range of impact parameters. They are compared to the predictions of the Isospin
Quantum Molecular Dynamics model using three different parametrisations of the
equation of state. We show that such highly accurate data provide stringent
test for microscopic transport models and can potentially constrain separately
the stiffness of the nuclear equation of state and the momentum dependence of
the nuclear interaction.
