  We report the detection of the Pb I 4057.8A line in the very metal-poor
([Fe/H]=-2.7), carbon-rich star, LP625-44. We determine the abundance of Pb
([Pb/Fe] = 2.65) and 15 other neutron-capture elements. The abundance pattern
between Ba and Pb agrees well with a scaled solar system s-process component,
while the lighter elements (Sr-Zr) are less abundant than Ba. The enhancement
of s-process elements is interpreted as a result of mass transfer in a binary
system from a previous AGB companion, an interpretation strongly supported by
radial velocity variations of this system.
  The detection of Pb makes it possible, for the first time, to compare model
predictions of s-process nucleosynthesis in AGB stars with observations of
elements between Sr and Pb. The Pb abundance is significantly lower than the
prediction of recent models (e.g., Gallino et al. 1998), which succeeded in
explaining the metallicity dependence of the abundance ratios of light
s-elements (Sr-Zr) to heavy ones (Ba-Dy) found in previously observed
s-process-enhanced stars. This suggests that one should either (a) reconsider
the underlying assumptions concerning the 13C-rich s-processing site
(13C-pocket) in the present models, or (b) investigate alternative sites of
s-process nucleosynthesis in very metal-poor AGB stars.
