Resistivity, giant magnetoresistance and thermopower in La0.7Sr0.3MnO3 showing a large difference in temperatures corresponding to the ferromagnetic transition and the insulator-metal transition

La0.7Sr0.3MnO3 samples prepared by heating the precursor gel at different temperatures in the 873 - 1473 K range show nearly the same ferromagnetic transition temperature (T-c approximate to 392+/-4 K), but the insulator-metal like transition temperatures (T-p) are significantly lower (approximate to 170 K) than the corresponding T(c)s in the samples annealed at lower temperatures (873 K and 1073 K). Magnetoresistance shows a peak only in the sample where T-p approximate to T-c. Thermopower (S) is large and negative for the samples annealed at lower temperatures, but it is low, exhibiting a change of sign with temperature for the sample annealed at 1473 K. Copyright (C) 1996 Published by Elsevier Science Ltd