  The strongly exchange enhanced Pauli paramagnet LaCo$_9$Si$_4$ is found to
exhibit an itinerant metamagnetic phase transition with indications for
metamagnetic quantum criticality. Our investigation comprises magnetic,
specific heat, and NMR measurements as well as ab-initio electronic structure
calculations. The critical field is about 3.5 T for $H||c$ and 6 T for $H\bot
c$, which is the lowest value ever found for rare earth intermetallic
compounds. In the ferromagnetic state there appears a moment of about 0.2
$\mu_B$/Co at the $16k$ Co-sites, but sigificantly smaller moments at the 4d
and $16l$ Co-sites.
