  We have studied the influence of a magnetic field on the thermodynamic
properties of Ca$_{2-x}$Sr$_{x}$RuO$_4$ in the intermediate metallic region
with tilt and rotational distortions ($0.2\leq x \leq 0.5$). We find strong and
anisotropic thermal expansion anomalies at low temperatures, which are
suppressed and even reversed by a magnetic field. The metamagnetic transition
of Ca$_{1.8}$Sr$_{0.2}$RuO$_4$ is accompanied by a large magnetostriction.
Furthermore, we observe a strong magnetic-field dependence of $c_p/T$, that can
be explained by magnetic fluctuations.
