The location and consequences of linked seams of conical intersections, conical intersections of states (J,K) and (K,L), are considered. We show that this class of conical intersections gives rise to the induced geometric phase effect, as a result of which the derivative couplings may be double-valued. This double-valuedness has important consequences, some limiting others not. We show, using an analysis based on branch cuts, that if the derivative coupling is double-valued, its circulation, its line integral about a closed loop, is not a unique function of the path, being starting point dependent. On the other hand the change from single-valued to double-valued derivative couplings can be used to search for linked intersections. (C) 2003 American Institute of Physics.