Evidence for density-wave domain structure in a mixed-band low-dimensional organic conductor

We have used angular-dependent magnetoresistance to probe the anomalous low-temperature state in the two-band (quasi-one- and -two-dimensional) organic conductor family α-(BEDT-TTF${)}_2$MHg(SCN${)}_4$, where BEDT-TTF stands for bis(ethylenedithio)tetrathiafulvalene. Our results provide strong evidence for a mixed state of both normal-metallic and Peierls-like domains with correspondingly different electronic structure. The different attributes of these coexisting domains are shown to be responsible for the complex magnetotransport phenomena in these materials, including the strong hysteretic behavior and the quantum-oscillation wave forms.