Direct Observation of Charge Order in an Epitaxial [Formula presented] Film

The first direct observation of charge order of [Formula presented] and [Formula presented] by resonant x-ray scattering experiments in an epitaxial film of [Formula presented] is reported. A quantitative value of [Formula presented] was obtained. The temperature dependence of the charge order deviates significantly from those of the magnetic moment and crystallographic structure. This might be an indication of a difference in their fluctuation time scales. These observations are discussed in terms of the temperature-driven metal-insulator transition in the [Formula presented] family. © 2002 The American Physical Society.