  Transport measurements on thin films of NdNiO$_3$ reveal a crossover to a
regime of pronounced nonlinear conduction below the well-known metal-insulator
transition temperature. The evolution of the transport properties at
temperatures well below this transition appears consistent with a gradual
formation of a gap in the hole-like Fermi surface of this strongly correlated
system. As $T$ is decreased below the nominal transition temperature, transport
becomes increasily non-Ohmic, with a model of Landau-Zener breakdown becoming
most suited for describing $I(V)$ characteristics as the temperature approaches
2~K.
