  We report on the evolution of the thermal metal-insulator transition in
polycrystalline samples of Nd$_2$Ir$_2$O$_7$ upon hole-doping via substitution
of Ca$^{2+}$ for Nd$^{3+}$. Ca substitution mediates a filling-controlled
Mott-like transition with minimal resolvable structural changes and without
altering site symmetry. Local structure confirms that Ca substitution does not
result in local chemical phase separation, and absorption spectroscopy
establishes that Ir cations maintain a spin-orbit entangled electronic
configuration. The metal-insulator transition coincides with antiferromagnetic
ordering on the Ir sublattice for all measured samples, and both decrease in
onset temperature with Ca content. Weak low-temperature upturns in
susceptibility and resistivity for samples with high Ca content suggest that Nd
sublattice antiferromagnetism continues to couple to carriers in the metallic
regime.
