A cosmetic preparation which comprises a sunscreen agent for protecting the human epidermis against UV light in the range from 280 to 400 nm, which comprises, in a cosmetically suitable carrier, alone or together with compounds which absorb in the UV region and are known for cosmetic preparations, as photostable UV-A filters, effective amounts of compounds of the formula I ##STR1## where R.sup.1, R.sup.2 and R.sup.3 are hydrogen or aliphatic or cycloaliphatic radicals each having up to 18 carbon atoms, it being possible for any two of the radicals R.sup.1, R.sup.2 and R.sup.3 together to form a 5- or 6-membered ring, and R.sup.4 and R.sup.5 are an unsubstituted or substituted aromatic or heteroaromatic radical having 5 to 12 ring atoms, and R.sup.5 can additionally be hydrogen.