We report detailed measurements of the electrical resistivity, Seebeck coefficient, and differential scanning calorimetry across the metal-insulator (MI) transition ( T MI ≊205 K) of NdNiO 3 . As in the isostructural oxide PrNiO 3 , the transition is extremely hysteretic, consistent with the first-order character of the transition. Analysis of the data shows that metallic and nonmetallic phases coexist in a broad temperature interval (≊70 K). The electrical resistivity and Seebeck coefficients of the metallic state display a clear linear temperature dependence. These properties can be rationalized in terms of a Fermi gas picture of rather heavy electrons (effective mass of about 6 m 0 ). Some physical parameters of the gas are predicted. The entropy change across the MI transition has been measured and it has been used to predict a strong pressure dependence of the MI transition temperature: dT MI /dP≊-4.8 K/kbar.