PrFe₄P₁₂ exhibits a heavy-electron-like behavior and a phase transition to an antiferro-quadrupolar ordering state at the lowest temperature. Inelastic neutron scattering experiments for a polycrystalline sample revealed a quasielastic response and no crystal-field excitation in the heavy-electron state. It is in contrast to the observed sharp crystal-field excitations in PrInAg₂ considered as a candidate of a quadrupolar Kondo system. In the ordered phase, sharp peaks at 1.4 and 3.0 meV are superimposed on the broad spectrum. These sharp excitations are consistent with the localized behavior of the 4f electrons in the antiferro-quadrupolar ordered phase.

PACS numbers: 71.27.+a, 71.45.Gm, 75.30.Mb, 78.70.Nx