  The unusual features of topological semimetals arise from its nontrivial band
structure. The impact of strong electron correlations on the topological states
remains largely unexplored in real materials. Here, we report the
magnetotransport properties of YbCdSn single crystals. We found two fundamental
experimental evidences of electron correlations through magnetic susceptibility
and specific heat. The electron correlations in this compound lead to an
intermediate valence state and enhance the effective mass of the charge
carriers. This correlated state exhibits large nonsaturating magnetoresistance,
low carrier density, magnetic field induced metal-semiconductor-like crossover
and a plateau in resistivity at low temperatures. This compound also shows a
cusp-like magnetoconductivity at low magnetic field which indicates the
presence of weak antilocalization effect. Our band structure calculations of
Yb$^{2+}$ state predict YbCdSn to be a topological nodal-line semimetal.
