  The electron transport properties of a four-terminal molecular device are
computed within the framework of density functional theory and non-equilibrium
Keldysh theory. The additional two terminals lead to new properties, including
a pronounced negative differential resistance not present in a two-terminal
setup, and a pseudo-gating effect. In general, quantum interference between the
four terminals and the central molecule leads to a complex non-linear behavior,
dependent on the alignment of individual molecular states under bias and their
coupling to the leads.
