This recent article discusses a series of isostructural complexes across the lanthanides using a multidentate ligand. In these structures, the lanthanides are all eight-coordinate, bonded to all oxygen donors. Copious structural data is presented that provides excellent experimental verification of the lanthanide contraction.
I have not used this yet in class, but it would seem to be an excellent paper, destined to be a classic in the field. Alternatively, the paper could form the basis for a good problem set question.