Syngenta (>> Syngenta AG) was up 11 percent, the top STOXX Europe 600 <.STOXX> riser after U.S. regulator CFIUS cleared ChemChina's $43 billion takeover of Syngenta, removing significant uncertainty over whether the acquisition of the world's largest pesticides maker will be completed.
The stock contributed 32 points to Switzerland's SMI <.SSMI> index, and single-handedly accounted for its gains. The index was up 0.3 percent, outperforming slight falls on most other European stock indexes.
The STOXX 600 was down 0.1 percent, extending losses after posting its biggest weekly drop since June on Friday, falling away after it hit its highest level since Britain voted to leave the European Union.
Elsewhere, shares of Teleperformance (>> Téléperformance), an investor favourite following the UK's Brexit vote, hit a record high.
(Reporting by Alistair Smout)