Magnetic field studies of the peculiar electronic state in the /spl alpha/-(BEDT-TTF)/sub 2/MH/sub g/(SCN)/sub 4/ family

Summary form only given. The variety of magnetoresistance (MR) anomalies exhibited by the members of the /spl alpha/-(BEDT-TTF)/sub 2/MH/sub g/(SCN)/sub 4/ family with M=Tl, K or Rb is reviewed in the connection with possible modification of their electronic structure at low temperatures. Special attention is paid to the angular MR oscillations (AMRO) which provide indispensable information about the Fermi surface (FS). Two different types of AMRO are observed above and below the phase transition temperature, T/sub p/, respectively. The high-temperature AMRO are associated with the cylindrical FS enabling us to deduce the cylinder cross-section. At the same time, the low-temperature AMRO reveal an occurrence of a specific plane in the electronic system indicating that a new periodicity arises below T/sub p/. The cylindrical AMRO can be restored by high magnetic field or high pressure thus confirming the re-entrance into the high-temperature state. We present the results on the low temperature AMRO in all the three salts and analyze them in view of possible changes in the electronic system. Other peculiarities of both the semiclassical MR and quantum oscillations are also discussed within the proposed model.