The behaviour of lithium at high metallicity in the Milky Way --
  Selection effects in the samples and the possible role of atomic diffusion
  We revisit large spectroscopic data sets for field stars from the literature
to derive the upper Li envelope in the high metallicity regime in our Galaxy.
We take advantage of Gaia EDR3 data and state-of-the-art stellar models to
precisely determine the position of the sample dwarf stars in the
Hertzsprung-Russell diagram. The highest Li abundances are found in field
metal-rich warm dwarfs from the GALAH survey, located on the hot side of the
Li-dip. Their mean Li value agrees with what was recently derived for warm
dwarfs in metal-rich clusters, pointing towards a continuous increase of Li up
to super-solar metallicity. However, if only cool dwarfs are considered in
GALAH, as done in the other literature surveys, it is found that the upper Li
envelope decreases at super-solar metallicities, blurring the actual Li
evolution picture. We confirm the suggestion that field and open cluster
surveys that found opposite Li behaviour in the high metallicity regime do not
sample the same types of stars: The first ones, with the exception of GALAH,
miss warm dwarfs that can potentially preserve their original Li content.
Although we can discard the bending of the Li upper envelope at high
metallicity derived from the analysis of cool star samples, we still need to
evaluate the effects of atomic diffusion on warm, metal-rich early-F and late-A
type dwarfs before deriving the actual Li abundance at high metallicity.
