  The electrical resistance, Hall resistance and thermoelectric power of the
Ising-like antiferromagnet UIrSi3 were measured as functions of temperature and
magnetic field. We have observed that the unequivocally different characters of
first-order and second-order magnetic phase transitions lead to distinctly
different magnetotransport properties in the neighborhood of corresponding
critical temperatures and magnetic fields, respectively. The magnetic
contributions to the electrical and Hall resistivity in the antiferromagnetic
state, and the polarized and normal regimes of paramagnetic state are driven by
different underlying mechanisms. Results of detailed measurements of
magnetotransport in the vicinity of the tricritical point reveal that the
Hall-resistivity steps at phase transitions change polarity just at this point.
The jumps in field dependences of specific heat, electrical resistivity, Hall
resistivity and Seebeck coefficient at the first-order metamagnetic transitions
indicate a Fermi surface reconstruction, which is characteristic of a
magnetic-field induced Lifshitz transition. The presented results emphasize the
usefulness of measurements of electrical- and thermal-transport properties as
sensitive probes of magnetic phase transformations in antiferromagnets
sometimes hardly detectable by other methods.
