  The conductance in an extended multiband Hubbard model describing linear
arrays of up to ten quantum dots is calculated via a Lanczos technique. A
pronounced suppression of certain resonant conductance peaks in an applied
magnetic field due to a density-dependent spin-polarization transition is
predicted to be a clear signature of a coherent ``molecular'' wavefunction in
the array. A many-body enhancement of localization is predicted to give rise to
a {\em giant magnetoconductance} effect in systems with magnetic scattering.
