Electron-spin-resonance and dc conductivity data show a thermal-history-dependent transition at 240 K in pressed pellets of ${\mathrm{ClO}}_4^{\mathrm{-}}$-doped poly(3-methylthiophene) (P3MT). We discuss the possibility of this transition to be a Peierls transition from a room-temperature-metallic to a charge-density-wave state driven by anions ordering at this temperature. Below 100 K, dc conductivity shows a change from linear to exponential decay. Nonlinear conductivity has also been observed in this system for very low electric fields.

• Received 22 February 1994

DOI:https://doi.org/10.1103/PhysRevB.50.3648