Difluorophenylpyrimidylpyridine derivatives of the formula (I) ##STR1## wherein X is N and Y is CH or X is CH and Y is N;R.sup.1 and R.sup.2 are identical or different and area) an unbranched or branched alkyl chain having 1 to 20 carbon atoms, whereaa) one or more non-adjacent and non-terminal CH.sub.2 groups may be replaced by --O--, --CO--O--, --O--CO--, --O--CO--O-- or --Si(CH.sub.3).sub.2 --, and/orab) one or more H atoms may be replaced by F, and/orac) the terminal CH.sub.3 group may be replaced by one of the following chiral groups (optically active or racemic): ##STR2## R.sup.3, R.sup.4 and R.sup.5 are identical or different and are hydrogen or a straight-chain or branched alkyl radical having 1-16 carbon atoms (with or without an asymmetrical carbon atom), where, in addition, one or more non-adjacent non-terminal CH.sub.2 groups may be replaced by --O--, and/or where one or more H atoms of the alkyl radical may be substituted by --F; R.sup.4 and R.sup.5 may alternatively together be --(CH.sub.2).sub.4 -- or --(CH.sub.2).sub.5 -- if they are bonded to a dioxolane system,are suitable as components, in particular, of ferroelectric liquid-crystal mixtures.