LITHIUM AND METAL ABUNDANCES IN LONG-PERIOD AM BINARIES

High signal-to-noise CCD spectra of three bright, long period Am binar ies (HD 108651, HD 116657 and HD 138213) have been obtained and the at mospheric abundances of identified chemical elements were studied. We found HD 116657 to be a new candidate as a Li deficient, long period A m binary, in addition to 16 Ori. While HD 108651 and HD 116657 have pr onounced Am characteristics, HD 138213 is just a mild Am star. These s tars were further studied in a more general context related to the rol e of binarity in CP phenomenon. It was found that both Li abundance an d the equivalent with ratio Ca I 6718/Fe I 6679 are more peculiar in s ystems with more pronounced eccentricities. Such behaviour is the oppo site of what was previously found in Ap binaries and their anomalies. It indicates that tidal effects are of crucial importance in driving C P phenomena.