It is a remarkable well-stablished fact that the light velocity in vacuum, $c \simeq 3.10^8 m/s$ is the upper limit for the velocity of ordinary matter, never to be achieved.
It is also well-stablished that in different media, the light velocity 'varies': in a higher density medium, for propagating from point A to B, light passes trough electrons and multiple particles, being absorbed and re-emited by some of these particles, than 'slowing down' the process in average, being the net velocity smaller than $c$.
My question is: would there exist known 'materials' (particles or of any kind) to propagate faster than light in such (any) kind of medium (in which light velocity is less than $c$)? It is not against GR and SR, as long as this particles do not exceed $c$.
This is a similar question to this one,
but not considering a man as subject (any material), and mirrors.
This point out to an 'intuitive view' of mine, that in terms of interaction of such particle/materials with the medium it should be considered 'lighter' than light (the interaction)...