MAGNETIC-ORDERING AND FERMI-SURFACE EFFECTS IN THE LOW-DIMENSIONAL ORGANIC CONDUCTOR ALPHA-(BEDT-TTF)(2)RBHG(SCN)(4)

Members of the family of low-dimensional organic conductors alpha-(BED T-TTF)2MHg(SCN)4, with M = K, Rb, Tl, or NH4, have a Fermi surface (FS ) consisting of both quasi-two-dimensional (Q2D) closed hole orbits an d quasi-one-dimensional (QID) open orbits. The charge transfer salts w ith M = K, Rb, and Tl undergo an antiferromagnetic ordering transition at about 10 K, which results in a density wave ground state. We have performed magnetoresistance (MR) measurements on alpha-(BEDT-TTF)2RbHg (SCN)4 in order to understand details of the FS, and the nature of the interaction of the FS with the magnetic ordering in this material.