We report narrow structures observed in the population of the intermediate level of a two-photon transition in a fast beam of metastable 20Ne* atoms. Steady-state theory provides a description of two coherent processes leading to population trapping. Both processes proceed via the ordinary two-photon coherence. One is then completed with a reversed-time ordering of the last two interactions, leading to a dispersive variation of the population of the real intermediate level, the other creates a hole in this population. A narrow Doppler profile enhances the visibility of these processes.