The organic conductor (TMTSF)
2
CIO
4
exhibits unusual magnetotransport effects below 30 K. The resistivity and thermopower have large, anisotropic changes in a magnetic field, whereas the thermal conductivity is hardly affected. At lower temperature (
T
≤ 5 K) a magnetic field applied along the
c
* direction causes a phase transition from a metallic, non-magnetic state to a semimetallic, magnetic state. This orbitally induced transition appears to be unique in nature. Above the threshold field for this transition steps in the Hall resistance are observed, suggestive of the quantum Hall effect. In this paper we review the magnetotransport experiment in these materials and discuss the possible origins of the unusual phenomena observed.
