We present the first detailed chemical abundances for three giant stars which
are candidate members of the Canis Major overdensity, obtained by using
FLAMES-UVES at VLT. The stars, in the background of the open cluster NGC 2477,
have radial velocities compatible with a membership to this structure. However,
due to Galactic disc contamination, radial velocity by itself is unable to
firmly establish membership. The metallicities span the range -0.5 < [Fe/H] <
+0.1. Assuming that at least one of the three stars is indeed a member of CMa
implies that this structure has undergone a high level of chemical processing,
comparable to that of the Galactic disc. The most metal-rich star of the
sample, EIS 6631, displays several abundance ratios which are remarkably
different from those of Galactic stars: [alpha/Fe] ~-0.2, [Cu/Fe] ~+0.25,
[La/Fe]~+0.6, [Ce/Fe]~+0.8 and [Nd/Fe]~+0.6. These ratios make it likely that
this star was formed in an external galaxy.Comment: 4 pages, 4 figures, accepted for publication in A&A letter
