  Identifying the fingerprints of the Mott-Hubbard metal-insulator transition
may be quite elusive in correlated metallic systems if the analysis is limited
to the single particle level. However, our dynamical mean-field calculations
demonstrate that the situation changes completely if the frequency dependence
of the two-particle vertex functions is considered: The first non-perturbative
precursors of the Mott physics are unambiguously identified well inside the
metallic regime by the divergence of the local Bethe-Salpeter equation in the
charge channel. At low temperatures this occurs in the region where incoherent
high-energy features emerge in the spectral function, while at high
temperatures it is traceable up to the atomic-limit.
