Despite nearly three decades of materials development, the transport properties in the 'metallic state' of the so-called conducting polymers are still not typical of conventional metals^{1, 2, 3, 4, 5, 6, 7}. The hallmark of metallic resistivity—a monotonic decrease in resistivity with temperature—has not been obtained at temperatures over the full range below room temperature; and a frequency dependent conductivity, (), typical of metals has also not been observed. In contrast, the low-temperature behaviour of 'metallic' polymers has, in all previous cases, exhibited an increase in resistivity as temperature is further decreased, as a result of disorder-induced localization of the charge carriers^{1, 2, 3, 4}. This disorder-induced localization also changes the infrared response such that () deviates from the prediction of Drude theory^{5, 6, 7}. Here we report classic metallic transport data obtained from truly metallic polymers. With polyaniline samples prepared using self-stabilized dispersion polymerization⁸, we find that for samples having room-temperature conductivities in excess of 1,000 S cm^-1, the resistivity decreases monotonically as the temperature is lowered down to 5 K, and that the infrared spectra are characteristic of the conventional Drude model even at the lowest frequencies measured.

1. Department of Physics, Pusan National University, Busan 609-735, Korea
   
2. Center for Polymers and Organic Solids, University of California at Santa Barbara, Santa Barbara, California 93106-5090, USA
   
3. Department of Molecular Science and Technology, Ajou University, Suwon 442-749, Korea
   
4. *These authors contributed equally to this work

Correspondence to: Kwanghee Lee^1,2,4 Correspondence and requests for materials should be addressed to K.L. (Email: kwhlee@pusan.ac.kr) and S.-H.L. (Email: hyja@ajou.ac.kr