Can I use combine on a property in an @Observable class?

As the title suggests, I have a class marked with @Observable. Within the class I have multiple var's. When one of my var's changes (formation), I want to run an updateOrCreateContent(). I had thought I could just do this with a bit of combine, but I'm struggling to get it working... The code below has a compile error at $formation When I mark formation @Published, it generates a different compile error: "Invalid redeclaration of synthesized property '_formation'"

any help appreciated thanks

class LayoutModel {
    
    var players: [Player] = []
    var formation: Formation = .f433
    var cancellables = Set<AnyCancellable>()

    
    init(players: [Player], formation: Formation) {
        self.players = players
        self.formation = formation
        updateOrCreateContent()

        $formation.sink(receiveValue: { _ in
            self.updateOrCreateContent()
        })
        .store(in: &cancellables)

}