  Low temperature behavior of the electronic specific heat $C(T)$ in the mixed
state is by the self-consistent calculation of the Eilenberger theory. In
addition to $\gamma T$-term ($\gamma$ is a Sommerfeld coefficient), $C(T)$ has
significant contribution of $T^2$-term intrinsic in the vortex state. We
identify the origin of the $T^2$-term as (i) V-shape density of states in the
vortex state and (ii) Kramer-Pesch effect of vortex core shrinking upon
lowering $T$. These results both for full-gap and line node cases reveal that
the vortex core is a richer electronic structure beyond the normal core
picture.
