  Magnetic quantum oscillations (MQO) of Hall coefficient are measured in
rare-earth tritelluride TmTe$_{3}$ and shown to be much stronger and persist to
higher temperature than the Shubnikov oscillations. It is general for MQO in
strongly anisotropic metals, and the combined measurements of Hall and diagonal
magnetoresistance provide useful informations about the electronic structure.
The ratio of their MQO amplitudes depends linearly on magnetic field, and its
slope gives a simple and accurate measurement tool of the electron mean free
time and its temperature dependence.
