We discuss the primordial nucleosynthesis of intermediate-mass nuclei up to A = 28 in the neutron-rich and proton-rich environments produced by baryon-number-inhomogeneous big bang models. We find that there could be several observational signatures of such neutron-rich and proton-rich primordial nucleosynthesis if sufficiently accurate isotopic and elemental abundance ratios could be measured for extremely metal-poor stars. These observations could also provide important information about the degree of baryon-number inhomogeneity at the time of primordial nucleosynthesis.

We show that primordial nucleosynthesis in baryon-inhomogeneous big-bang models can lead to significant heavy-element production while still satisfying all of the light-element abundance constraints including the low lithium abundance observed in Population II stars. The parameters which admit this solution arise naturally from the process of neutrino-induced expansion of baryon inhomogeneities prior to the epoch of nucleosynthesis. These solutions entail a small fraction of baryons (≲2%) in very high density regions with local baryon to photon ratio ηh ≃ 10-4, while most baryons are at a baryon-to-photon ratio which optimizes the agreement with light-element abundances. This model would imply a unique signature of baryon inhomogeneities in the early universe, evidenced by the existence of primordial material containing heavy-element products of proton and alpha-burning reactions with an abundance of [Z] ∼ -6 to -4.