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 ($0.2leq x leq 0.5$). 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.
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