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We have measured electrical and magnetic properties of single crystals of Sb 2Ϫx Mn x Te 3 with x ϭ0 -0.045 at temperatures of 2 K to 300 K. Hall effect measurements indicate that each manganese atom donates approximately one hole to the valence band. The magnetic susceptibility is paramagnetic down to 2 K, and both Curie-Weiss and Brillouin analyses show that manganese substitutes for Sb and takes the Mn 2ϩ state with Sϭ5/2. Contrary to the case of III-V host matrices, manganese does not stimulate ferromagnetic order in the family of bulk layered V 2 -VI 3 diluted magnetic semiconductors, at least in the range of magnetic impurity and carrier concentrations studied here.

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Single crystals of Sbl.5Bi0.5Te3 doped with Ag atoms ( c A~= 0-3.5 x 10'9atoms/cm3) were characterized by X-ray diffraction, measurement of reflectance in the plasma resonance frequency region, Hall coefficient, electrical conductivity, Seebeck coefficient and the figure of merit. It was found that Ag atoms in the crystal structure of Sbl sBio,5Te3 behave like acceptors; up to the concentration of c~g 1.7 x loL9 atoms/cm3 they increase the hole concentration, whereas in the concentration region of C A~ (1.7-3.5) x 1019atoms/cm3 the hole concentration does not change. The incorporation of Ag atoms into the Sbl.5Bio5Te3 crystal structure results in a decrease in the elementary cell volume and a decrease in the value of figure ofmerit. The increase in the hole concentration is ascribed to the formation of substitutional defects of Ag&, or Ag',,. Besides these defects the formation of interstitial ions of Ag: and four-layer-lamellae of the type [Ago.5Sbo.5]-Te-[Ago.5Sbo.5]-Te is suggested.