Michel Piccoli was a French actor of the generation of Philippe Noiret, Jean Rochefort and yes, Yves Montand.
Of note is his work with Marco Ferreri (Dillinger Is Dead, La Grande Bouffe, The Last Woman and Don’t Touch the White Woman!); with Luis Buñuel (Diary of a Chambermaid Belle de jour, The Milky Way, The Discreet Charm of the Bourgeoisie and The Phantom of Liberty); and Jean-Luc Godard (Contempt).
In The Milky Way (1969) he plays Marquis de Sade.
Then there is the iconic La Grande Bouffe (1973), the story of three bourgeois men who decide to eat themselves to death.
Later I saw Themroc (1973), one of the strangest counterculture films where he played opposite the tragic but delightful Patrick Dewaere.
Watching clips on YouTube, you see him with Romy Schneider in The Things of Life (1970), my god what a beautiful woman she was.