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PtSn4 and WTe2 single crystals were grown, and the resistivity was studied in the temperature range from 4.2 to 80 K in various magnetic fields up to 10 T in detail. It is suggested that the observed quadratic temperature dependence of the electrical resistivity at low temperatures in zero field can be due to, in addition to electron-electron scattering, the "electron-phonon-surface" interference scattering mechanism. The transition from high effective magnetic fields to weak ones, which is observed in compensated conductors with a closed Fermi surface, was proposed as a possible explanation for the minimum on the temperature dependence of the resistivity of PtSn4 and WTe2 in a magnetic field. The values of the mean free path of current carriers were estimated in these materials. [ABSTRACT FROM AUTHOR]

WTe2 and MoTe2 single crystals were grown, some of them were quenched, and the following properties were studied: electroresistivity in the temperature range from 1.8 to 300 K, magnetoresistivity at temperatures from 1.8 to 300 K in magnetic fields of up to 9 T. On the one hand, quenching leads to dramatic changes in the behaviour and value of the electroresistivity of MoTe2; the type of the electroresistivity changes from "semiconductor" to "metallic", and the electroresistivity values of MoTe2 before and after quenching differ by 8 orders of magnitude (!) at low temperatures. On the other hand, quenching is shown not to lead to significant changes in the behaviour and value of the electroresistivity of WTe2. A relatively small increase in the electroresistivity of quenched WTe2 at low temperatures can be associated with the scattering of current carriers by structural defects. The magnetoresistivity of MoTe2 increases from 7 to 16% in a field of 9 T at a temperature of 12 K as a result of quenching. The magnetoresistivity of WTe2 is shown to reach ∼1700% in a field of 9 T at 2 K. The behaviour of the magnetoresistivity of non-quenched samples is typical for compensated conductors with a closed Fermi surface. [ABSTRACT FROM AUTHOR]

Ni-Mn-Ga based compounds are of great interest due to their magneto- and temperature operated shape memory. To obtain new results on their electronic structure, we studied the low-temperature kinetic properties and the structure of Ni-Mn-Ga alloys at temperatures T≪ T M, T C ( T M is the temperature of the martensitic transition and T C the temperature of the magnetic (Curie) transition, which are both close to room temperature). Ordered (cast) and disordered samples, having a nanocrystalline substructure, were investigated. The galvanomagnetic and electrical properties were measured in the temperature interval from 2 to 80 K and in magnetic fields of up to 15 T. We find that the electrical and the high-field properties of these alloys strongly change due to the transition into the nanocrystalline state. [ABSTRACT FROM AUTHOR]