[Mathieu]

I usually find it suspicious when the preflop raiser checks on the flop HU. It often means a set, but it can also mean unimproved overcards.

I would bet the flop and fold to a check raise (the check raise bluff in this spot is too rare to worry about it).

I would definitely bet the turn again and fold to a check raise, as I think someone who would be willing to check raise semi bluff in this spot would also keep the lead on the flop.

I bet the river and call a raise.