This letter reports on unique room temperature organic magnetoresistance (OMAR) in the disordered polyaniline/silicon polymer nanocomposites in the variable range hopping regime. A transition from positive to negative OMAR was observed around 5.5?T. The theoretical analysis revealed that both wave-function shrinkage model and forward interference model contributed to the positive OMAR and only forward interference model was responsible for the observed negative OMAR. The obtained positive OMAR is well explained by the introduced localization length a0, density of states at the Fermi level (N(EF)), and average hopping length Rhop; and the negative OMAR is interpreted by the quantum interferenceeffect.
