  We report field and temperature dependent measurements of the thermoelectric
power (TEP) across the pseudo-metamagnetic transition (MMT) in CeRu$_2$Si$_2$.
We applied the thermoelectric gradient parallel and perpendicular to the field
along the c axis of the tetragonal crystal which is the easy magnetization
axis. At the MMT at H$_m$=7.8 T, a strong anomaly in the TEP is observed for
both configurations with opposite signs. The anomaly at Hm becomes a cascade of
anomalies at very low temperature which seems to be a generic feature of the
TEP at a change in the topology of the Fermi surface (FS) in heavy Fermion
multiband systems. Simultaneously, quantum oscillations in the magnetic field
dependence of the TEP are observed for both configurations below and above the
MMT.
