England's Matthew Carley will referee the Heineken Champions Cup semi-final between La Rochelle and Leinster at Stade Marcel Deflandre on Sunday, 2 May.
Carley also took charge of Leinster's win over Exeter in the quarter-final earlier this month.
Meanwhile England’s Wayne Barnes is the man in the middle for the all-French semi-final between Toulouse and Bordeaux-Bègles at Stade Ernest Wallon on Saturday May 1st.
Pascal Gauzère of France will oversee the Challenge Cup semi-final between Leicester Tigers and Ulster at Mattioli Woods Welford Road on April 30th while Andrew Brace heads an all Irish officiating team for the second semi-final between Bath and the 2016 winners, Montpellier, at the Recreation Ground on 1 May 1st.
Toulouse v Bordeaux-Bègles, Stade Ernest Wallon, 3pm (Wayne Barnes, Eng); La Rochelle v Leinster, Stade Marcel Deflandre, 3pm, (Matthew Carley, Eng).
Leicester Tigers v Ulster, Mattioli Woods Welford Road, 8pm, (Pascal Gauzère ,Fra); Bath v Montpellier, Recreation Ground (8pm) (Referee: Andrew Brace; Assistant referees: Frank Murphy, Chris Busby; TMO: Brian MacNeice; Citing Commissioner: Eugene Ryan (All Ireland).