The Seebeck coefficient of a metal is expected to display a linear
temperature-dependence in the zero-temperature limit. To attain this regime, it
is often necessary to cool the system well below 1K. We put under scrutiny the
magnitude of this term in different families of strongly-interacting electronic
systems. For a wide range of compounds (including heavy-fermion, organic and
various oxide families) a remarkable correlation between this term and the
electronic specific heat is found. We argue that a dimensionless ratio relating
these two signatures of mass renormalisation contains interesting information
about the ground state of each system. The absolute value of this ratio remains
close to unity in a wide range of strongly-correlated electron systems.Comment: 15 pages, including two figure