Paramagnetic Excited State of FeSi

The anomalous behavior of the temperature dependence of the susceptibility and specific heat of the intermetallic compound FeSi is reexamined from both an experimental and a theoretical point of view. It is shown that a consistent set of experimental data is obtained below a temperature of about 700\ifmmode^\circ\else\textdegree\fi{}K. An interpretation of the thermodynamic properties is given, based on a model that requires the existence of correlated magnetic excited states only a few hundred degrees above the nonmagnetic ground state. Other, more conventional models are also explored, and the reasons for their rejection are discussed.