  Aims: We report the discovery of a young lithium rich giant, HD 16771, in the
core-helium burning phase that does not seem to fit existing proposals of Li
synthesis near the luminosity function bump or during He-core flash. We aim to
understand the nature of Li enrichment in the atmosphere of HD 16771 by
exploring various Li enhancement scenarios. Methods: We have collected
high-resolution echelle spectra of HD 16771 and derived stellar parameters and
chemical abundances for 27 elements by either line equivalent widths or
synthetic spectrum analyses. Results: HD 16771 is a Li-rich
(log(n(Li))=+2.67+/-0.10 dex) intermediate mass giant star (M=2.4+/-0.1 Msun)
with age=0.76+/-0.13 Gyr and located at the red giant clump. Kinematics and
chemical compositions are consistent with HD 16771 being a member of the
Galactic thin disk population. The non-detection of 6Li(< 3%), a low carbon
isotopic ratio (12C/13C=12+/-2), and the slow rotation (vsini=2.8 km/s) all
suggest that lithium might have been synthesized in this star. On the contrary,
HD 16771 with a mass of 2.4 Msun has no chance of encountering luminosity
function bump and He-core flash where the possibility of fast deep-mixing for
Li enrichment in K giants has been suggested previously. Conclusions: Based of
the evolutionary status of this star, we discuss the possibility that 7Li
synthesis in HD 16771 is triggered by the engulfment of close-in planet(s)
during the RGB phase.
