  Aims: We aim at characterizing the inward transition from convective to
radiative energy transport at the base of the convective envelope of the
solar-like oscillator HD 52265 recently observed by the CoRoT satellite.
Methods: We investigated the origin of one specific feature found in the HD
52265 frequency spectrum. We modelled the star to derive the internal structure
and the oscillation frequencies that best match the observations and used a
seismic indicator sensitive to the properties of the base of the envelope
convection zone. Results: The seismic indicators clearly reveal that to best
represent the observed properties of HD 52265, models must include penetrative
convection below the outer convective envelope. The penetrative distance is
estimated to be $\sim0.95 H_P$, which corresponds to an extent over a distance
representing 6.0 per cents of the total stellar radius, significantly larger
than what is found for the Sun. The inner boundary of the extra-mixing region
is found at $0.800\pm0.004 R$ where $R=1.3 R_\odot$ is the stellar radius.
Conclusions: These results contribute to the tachocline characterization in
stars other than the Sun.
