  A 40-year-old puzzle in transition metal pentatellurides ZrTe$_5$ and
HfTe$_5$ is the anomalous peak in the temperature dependence of the
longitudinal resistivity, which is accompanied by sign reverses of the Hall and
Seebeck coefficients. We give a plausible explanation for these phenomena
without assuming any phase transition or strong interaction effect. We show
that due to intrinsic thermodynamics and diluteness of the conducting electrons
in these materials, the chemical potential displays a strong dependence on the
temperature and magnetic field. With that, we compute resistivity, Hall and
Seebeck coefficients in zero field, and magnetoresistivity and Hall resistivity
in finite magnetic fields, in all of which we reproduce the main features that
are observed in experiments.
