  Contrary to previous expectations, recent evolutionary models of
zero-metallicity stars show that the development of mixing episodes at the
beginning of the AGB phase allows low- and intermediate-mass stars to
experience thermal pulses. If these stars, like their metal-rich counterparts,
also experience partial mixing of protons from the H-rich envelope into the
C-rich layers at the time of the third dredge-up, an extensive neutron capture
nucleosynthesis leads to the production of s-process nuclei up to Pb and Bi.
Nucleosynthesis calculations based on stellar AGB models are performed assuming
a parameterized H-abundance profile below the convective envelope at the time
of the third dredge-up. Despite the absence of Fe-group elements, the large
neutron flux resulting from the 13C(alpha,n)16O reaction leads to an efficient
production of s-process elements starting from the neutron captures on the C-Ne
isotopes. Provided partial mixing of protons takes place, it is shown that
population III AGB stars should be enriched in s-process elementsand overall in
Pb and Bi.
