  The thermal conductivity of a quasiparticle (QP) system described by a
relativistic four-fermion interaction model in the presence of an external
magnetic field is calculated. It is shown that, for narrow width of
quasiparticles, the thermal conductivity, as a function of the applied magnetic
field, exhibits a kink behavior at a critical field $B_{c}\sim T^{2}$. The kink
is due to the opening of a gap in the QP spectrum at a critical magnetic field
$B_c$ and to the enhancement of the transitions between the zeroth and first
Landau levels. Possible applications of the results are discussed.
