  Tuning of electronic density-of-states singularities is a common route to
unconventional metal physics. Conceptually, van Hove singularities are realized
only in clean two-dimensional systems. Little attention has therefore been
given to the disordered (dirty) limit. Here, we provide a magnetotransport
study of the dirty metamagnetic system calcium-doped strontium ruthenate. Fermi
liquid properties persist across the metamagnetic transition, but with an
unusually strong variation of the Kadowaki-Woods ratio. This is revealed by a
strong decoupling of inelastic electron scattering and electronic mass inferred
from density-of-state probes. We discuss this Fermi liquid behavior in terms of
a magnetic field tunable van Hove singularity in the presence of disorder. More
generally, we show how dimensionality and disorder control the fate of
transport properties across metamagnetic transitions.
