Direct adiabatic temperature change as well as magnetic measurements were carried out on two different samples of ${\mathrm{Gd}}_5{\mathrm{Si}}_2{\mathrm{Ge}}_2$ composition for which calculations predicted a “giant” magnetocaloric effect (MCE). While magnetic measurements well reproduce published values, serving the basis for the predictions, direct adiabatic temperature change measurements show a significantly smaller MCE. The discrepancy can be interpreted on the basis of the thermodynamics of first order magnetic transitions.

• Received 23 November 1998

DOI:https://doi.org/10.1103/PhysRevLett.83.2262