  A hybrid spin-electron system on one-dimensional tetrahedral chain, in which
the localized Ising spin regularly alternates with the mobile electron
delocalized over three lattice sites, is exactly investigated using the
generalized decoration-iteration transformation. The system exhibits either the
ferromagnetic or antiferromagnetic ground state depending on whether the
ferromagnetic or antiferromagnetic interaction between the Ising spins and
mobile electrons is considered. The enhanced magnetocaloric effect during the
adiabatic demagnetization suggests a potential use of the investigated system
for low-temperature magnetic refrigeration.
