  Materials exhibiting large magnetoresistance may not only be of fundamental
research interest, but also can lead to wide-ranging applications in magnetic
sensors and switches. Here we demonstrate a large linear-in-field
magnetoresistance, $\Delta \rho/\rho$ reaching as high as $\sim$600$\%$ at 2 K
under a 9 Tesla field, in the tetragonal phase of a transiton-metal stannide
$\beta$-RhSn$_4$. Detailed analyses show that its magnetic responses are
overall inconsistent with the classical model based on the multiple electron
scattering by mobility fluctuations in an inhomogenous conductor, but rather in
line with the quantum effects due to the presence of Dirac-like dispersions in
the electronic structure. Our results may help guiding the future quest for
quantum magnetoresistive materials into the family of stannides, similar to the
role played by PtSn$_4$ with topological node arcs.
