ABSTRACT
A magnetoresistance (MR) of the well known TVO resistor temperature sensors has been studied at ultralow temperatures from approximately 0.8 K down to approximately 0.1 K under strong magnetic fields up to 8 T. A crossover from positive to negative MR with lowering temperature is found at weak magnetic fields. A zero MR-value at the magnetic field of 4 T, for example, is reached at T approximately 0.2 K. At sufficiently strong magnetic field the negative MR is suppressed and MR returns to positive values. A constant negative MR, which does not depend on the magnetic field from 2 to 8 T, is revealed at the lowest temperature T approximately 0.1 K. The observed behavior of the TVO sensor is explained basing on the model of hopping conduction via localized states in the weak localization regime.