The transverse magnetoresistance MR and thermoelectric power S of semiconductors having various regularity of crystal structure were investigated at high pressure P up to 30 GPa by synthetic diamond anvils. An approach is discussed for the investigation of pressure-induced semiconductor - metal phase transitions in a wide group of materials based on both the model of p-bonds and Peierls distortion of lattice and the experimental results of thermoelectric power (S) and transverse magnetoresistance (MR) measurements at high pressures up to 30 GPa. The technique of S and MR measurements up to 30 GPa at the synthetic diamond anvils have been applied for investigation of Hg-, Cd-, Zn-, Eu-, Sm-, In-, Ga- chalcogenides, Tellurium, Selenium, Iodine etc. with various morphology (crystal or powder) and regularity of lattice (from cuic sphalerite lattice to amorphous and molecular crystal Iodine) [1,2] It was found that S(P) behaviour describes the sign of prevailing charge carriers and the dependence of energy gap of electron structure on pressure for any type of lattice [1,2]. The influence of the sample isn't appreciable for S(P) data. For MR the type of chemical bonding and the regularity of lattice determine the sign and value of magnetoresistance and estimated mobility ( of charge carriers.The sign inversions of MR and S, established for these materials, determined the changes of the charge carriers type and the scattering processes at the electron structure transformations under pressure. The increase of MR and holes mobility under pressure found for Te and Se below the Semiconductor-Metal (S-M) transition [2] is consistent with the vanishing of band gaps [1, 3].
Cubic sphalerite ternary mercury chalcogenides, sphalerite with the 1/3 cation vacancies In2Te3, Ga2Te3, Ga2Se3, trigonal chain semiconductors Te, Se, Iodine, and chalcogenides (Zn, Cd, Sm, Eu) are analyzed in the frame of this approach. This work was partly supported by Russian Scientific Foundation for Basic
Research, grant N 98-03-32656.

References
[1]. V.V.Shchennikov et. al., Fizica Tverdogo Tela, 37, 1015 (1995);
37, 448 (1995); 38, 2680 (1996); 39, 1717 (1997); 42, 1004(2000)..
[2] V.V.Shchennikov, Phys.Stat.Sol.(b), 223, 561 (2001).

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