Context :

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 \sim 0.95 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 \pm 0.004 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 .