I n low-ohmic n-type ZnSe crystals with the room temperature specific resistance of (3 t o 5) rZ cm and electron concentration from 3 x 10l6 to 2 x 10l6Hall-effect, electrical conductivity, and charge carrier mobility is investigated in the temperature interval from 10 t o 300 K. The basic parameters of the samples are determined. It is found from the experimental data that the mobility is higher than the theoretical value in the investigated temperature range. It is argued that in the region of ionized impurity scattering this descrepancy between theory and experiment is due t o the inadequacy of known scattering based on the Born approximation, as for ZnSe this approximation is valid at T > 140 K, where the phonon scattering is predominant. To square the theory with the experiment in the phonon scattering region a polaron effect is taken into account, which manifests itself in renormalization of the carrier effective mass as well as in alteration of the mobility temperature dependence due t o the effect of screening of the interaction with polar vibrations. The theoretical consideration of this question is given which allows t o bring the theory and the experiment to a satisfactory correspondence.

Negative Magnetoresistance in p-CdSband D. N. NASLEDOV (a)Negative magnetoresistance is observed a t low temperatures in cadmium antimonide crystals with hole concentration 2 6 x 1W6 ~m -~. The results of the investigation of the field, angular and temperature dependences in the temperature range 2.2 to 77 O K of the magneto-resistance of copper, silver, germanium, and tin doped samples with carrier concentrations ranging from to 10l8 cm-3 are described. It is shown that the negative magnetoresistance is related probably to impurity band conduction. It is noted that the regularities observed, namely the quadratic dependence of the negative magnetoresistance on magnetic field strength at weak fields and saturation at strong fields, the linear change of the negative magnetoresistance with temperature and the isotropy of the effect have the same character as in AIV and AIIIBV crystals and conform qualitatively Toyozawa's theory.I n Kadmiumantimonidkristallen wird bei niedrigen Temperaturen und Locherkonzentrationen iiber 5 x lOl6 cm-S eine negative Magnetowiderstendsiinderung beobachtet. Es wurden die Ergebnisse der Untersuchungen der Feld-, Winkel-und Temperaturabhiingigkeit der Magnetowiderstandsinderung an Kupfer-, Silber-, Germanium-und Zinn-dotierten Proben bei Ladungstriigerkonzentrationen von 1W6 bis lo1* cm-S im Temperaturbereich 2,2 bis 77 O K beschrieben. Es wird gezeigt, da8 die negative Magnetowiderstandsilnderung wahrscheinlich mit einer Storbandleitung verbunden ist. Es wird bemerkt, da8 die beobachteten RegelmiiDigkeiten : die quadratische Abhiingigkeit der negativen Magnetowiderstandsiinderung von der magnetischen Feldstilrke bei schwachen Feldern und Siittigung bei starken Feldern, die lineare h d e r u n g der negativen Magnetowiderstandsiindernng mit der Temperatur und die Isotropie des Effekts den gleichen Charakter wie in den AIV-und AIIIBv-Kristallen besitzen und qualitativ mit der Toyozamaschen Theorie iibereinstimmen.

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