  Artificial confinement of electrons by tailoring the layer thickness has
turned out to be a powerful tool to harness control over competing phases in
nano-layers of complex oxides. We investigate the effect of dimensionality on
transport properties of $d$-electron based heavy-fermion metal
CaCu$_{3}$Ru$_{4}$O$_{12}$. Transport behavior evolves from metallic to
localized regime upon reducing thickness and a metal insulator transition is
observed below 3 nm film thickness for which sheet resistance crosses $h/e^{2}
\sim 25~$k$\Omega$, the quantum resistance in 2D. Magnetotransport study
reveals a strong interplay between inelastic and spin-orbit scattering lengths
upon reducing thickness, which results in weak antilocalization (WAL) to weak
localization (WL) crossover in magnetoconductance.
