Ambipolar transport in the field-suppressed superconducting state of quasi-one-dimensional Li$_{0.9}$Mo$_6$O$_{17}$

We present resistivity, Hall, Seebeck, and Nernst coefficient measurements in the range $0.4~K\leq T\leq 20$~K on single crystals of the quasi-one-dimensional (Q1D) metal, Li$_{0.9}$Mo$_6$O$_{17}$ with current along the Q1D metallic chains. At temperatures below the nominal superconducting transition temperature ($T_c=2$~K), a transition from hole-like ($\mu_0H< 1$~T) to electron-like ($\mu_0H\geq 2$~T) behavior is evidenced in the magnetotransport coefficients. Possible insights from these results into the nature of the mysterious density-wave order$^{a,b}$ responsible for the upturn in resistivity below $\sim 25$~K will be discussed. \vskip .1in \noindent $^a$ C. A. M. dos Santos {\it et al.}, Phys. Rev. Lett. {\bf 98}, 266405 (2007). \vskip .1in \noindent $^b$ X. Xu \emph{et al.}, Phys. Rev. Lett. {\bf 102}, 206602 (2009).