Thermomagnetic transport parameters have been measured in bismuth a t 80 O K and found to be strongly pressure-dependent. Results indicate that in addition to a decrease in the energy overlap, E,, there is an increased participation of a light hole band increasing the mobility of holes. The Nernst effect and the magneto-Seebeck effect are particularly sensitive t o changes in hole mobility. I n some orientations the Seebeck voltage in a field of 0.47 Wb/m* can change sign under uniaxial compression.I n Wismut wurden bei 80 O K die thermomagnetischen Transportparameter gemessen, und es wurde gefunden, daB sie stark druckabhiingig sind. Die Ergebnisse zeigen, daS zusiitzlich zu einer Verringerung der Energieuberlappung E, eine VergroSerung des Anteils eines Bandes leichter Locher auftritt, was die Beweglichkeit der Locher erhoht. Der Nernsteffekt und der Magneto-Seebeckeffekt sind besonders empfindlich gegeniiber hderungen der Locherbeweglichkeit. Bei einigen Orientierungen kann der Seebeckeffekt in einem Feld von 0,47 Wb/m2 unter einachsigem Druck sein Vorzeichen iindern.

In this paper we have calculated the expressions for the electrical conductivity and the thermoelectric power of thin metal films containing unionized or neutral impurities and having equal surface specularity parameters. The calculation is based on the solutions of the Boltzmann transport equation in the presence of a weak electric field and a small temperature gradient. The results indicate that the electrical conductivity decreases whereas the thermoelectric power increases.PACS 73.50 -Electronic transport phenomena in thin films.The electrical transport properties of thin metal films show a marked dependence [1-3] on the film thickness when the thickness is comparable with the bulk mean free path of the conduction electrons having the Fermi energy, E F. Most authors [4,5] have calculated the transport properties of thin metal films such as the electrical and the thermal conductivities and the thermoelectric power and the Peltier coefficient by assuming a spherical Fermi surface and a constant and isotropic relaxation time, z. However, these properties have also been calculated by using the assumption that the relaxation time has an energy dependence [6,7] of the form ~ = = a .E ~, while the surface specularity parameter is either the same or different for the two film surfaces and is constant or angle dependent.We now consider the important case in which the film, in addition to having somewhat rough surfaces (specularity parameter p >I 0), also contains neutral impurities in sufficiently large quantities so that the relaxation time for lattice scattering (~L-E-1/2) is comparable with the relaxation time for impurity scattering, ~. If the impurities happen to be neutral, vi is a constant [8]. In case of ionized impurities vi -E +3/2. The total relaxation time is then obtained by adding the scattering probabilities using Matthiessen's rule [9], that is 1 1 1 (1) --= --+ --.

In this paper analytical expressions for the electrical conductivity and thermoelectric power of thin metal films have been calculated for films containing ionized impurities and having unequal surface specularity parameters. The effects of alteration in the energy dependence of the electron relaxation time as well as unequal probabilities of scattering from the two surfaces are thus completely taken into account.PACS 73.50 -Electronic transport phenomena in thin films.The electrical transport properties of thin metal films are known to depend on the film thickness when the thickness is comparable to the bulk mean free path (m.f.p.) of the conduction electrons on the Fermi surface [i-3]. Assuming a constant and isotropic relaxation time v for electrons, transport coefficients for thin metal films have been calculated by several authors [4,5]. These properties have also been calculated under the assumption that the electron relaxation time ~ has an energy dependence[6, 7] of the form -r = a.E '~, while the surface specularity parameter is either same or different for the two film surfaces and is constant or angle dependent.If, however, the film contains ionized impurities in sufficiently large quantities so that the relaxation time for pure lattice scattering (VL ~ E-I~) is comparable with the relaxation time for ionized impurity scattering (z~ -E -3/2 ), then it is not possible to express the total relaxation time ~ in the above form but use has to be made of the Matthiessen's rule according to which the total relaxation time ~ can be expressed as [8](1) ! = • + !. T T I T LWhen a metal contains impurities, the field in the vicinity of the impurity atoms is in general different from that near the host atoms. The impurities, therefore, produce deviations from the periodicity of the potential and act as scattering centres for electrons. The total probability of scattering is obtained 64 -ll Nuovo Cimento D 951