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A new type of perturbation expansion in the mixing $V$ of localized orbitalswith a conduction-electron band in the $U\to\infty$ Anderson model ispresented. It is built on Feynman diagrams obeying standard rules. The localcorrelations of the unperturbed system (the atomic limit) are included exactly,no auxiliary particles are introduced. As a test, an infinite-order ladder-typeresummation is analytically treated in the Kondo regime, recovering the correctenergy scale. An extension to the Anderson-lattice model is obtained via aneffective-site approximation through a cumulant expansion in $V$ on thelattice. Relation to treatments in infinite spatial dimensions are indicated.Comment: selfextracting postscript file containing entire paper (10 pages)  including 3 figures, in case of trouble contact author for LaTeX-source or  hard copies (prep0994

Wick's Theorem and a New Perturbation Theory around the Atomic Limit of Strongly Correlated Electron Systems