  Persistent currents in a Moebius ladder are shown to be very sensitive to the
effects of intrachain interactions on the hopping of electrons between chains.
Their periodicity as a function of flux is doubled for strong enough repulsive
interactions because electrons cannot hop coherently between the chains and
have to travel along the full edge of the Moebius ladder, thus encircling the
flux twice. Mesoscopic devices that should enable one to observe these effects
are proposed.
