  It has been claimed that the absence of the bilayer splitting in the
high-temperature superconductor YBCO is a strong experimental indication that
there are no coherent quasiparticles present in the CuO planes. We study a pair
of strongly correlated planes which are connected by a hopping transfer
integral $t_{\perp}$ in the limit of large in-plane coordination number. The
effect of the correlation is incorporated in a dynamical mean-field theory,
where the Weiss field is determined by a two-site Hubbard Hamiltonian. We have
solved this problem by numerical techniques and present results for the
spectral function $\rho$ for relevant parameters of the model. For small
$t_{\perp}$ we find the coherent hoping between planes to be proportional to
the in-plane quasiparticle renormalisation.
