Thermoelectric characterization performed in this work on BaFe12O19 and BaTiO3 at 1 kHz involved anomalous negative capacitances over higher temperatures. By using alternating-current analysis techniques, we ratify our previous observations on their association with an inductive component leading to a resonance-type phenomenon. The dynamics of this latter, mostly expected to act rather over higher frequencies (>106 Hz), is carefully examined by using a simple but consistent model. Its large stretching to lower frequencies is found to be caused by the inner dynamics of the material dielectric response when becoming governed, over higher temperatures, by the material–electrode interface properties. © 2000 American Institute of Physics.