Ben Smith and Luke Whitelock impressed in their European rugby debuts but controversy continues to follow defending champions Saracens after an all-in brawl overshadowed their win over Munster.
Smith and Whitelock played their first match for Pau at the weekend, helping the French club to a 34-29 home win over the Cardiff Blues.
Former Highlanders Smith and Whitelock made immediate impressions. Smith, the 84 test veteran, laid on one of Pau's five tries for Pierre Nueno after a break from halfway followed by the perfectly-delivered pass.
Pau led 31-7 after 50 minutes but then had three players yellow carded which allowed Cardiff to stage a comeback. The win keeps Pau in contention for the Challenge Cup – Europe's second tier - knockouts.
Smith is on a six month stint in France before he moves to Japan while Whitelock has signed a three-year deal.
Sean Maitland scored for Saracens in their 15-6 Champions Cup victory over Munster but the main talking point from this ugly and ill-tempered match surrounds the investigation into events that sparked an all-in fracas.
One of Munster's medical staff is alleged to kicked off the 30-man brawl after making derogatory comments about England test hooker Jamie George's weight. Players from both teams, including those on the sideline, then engaged in a heated row.
The European governing body is now investigating the incident, saying: "Information will now be sought from the match officials and from both clubs, and EPCR will be making no further comment until the investigation has been completed."
The victory keeps Saracens in the hunt to defend their title but the brawl is another unwanted scene as they deal with the on-going fallout from their salary cap scandal.
Former Blues and All Blacks utility George Moala was in imperious form as he scored two of Clermont's eight tries in their 52-26 win over bumbling Bath.
Moala combined nicely with Isaia Toeava and former Chiefs No 8 Fritz Lee, with the crushing result underlining Clermont's credentials. Their round five fixture, when they host Ulster at the Stade Marcel Michelin, is now likely to decide who tops their pool.
James Lowe continued his form as he made five breaks and bagged one of seven tries for Leinster, who became the first team to book their Champions Cup quarterfinal spot with two rounds remaining after dishing out a repeat thrashing to Chris Boyd's Northampton Saints.
The 50-21 victory in Dublin followed last week's 46-16 drubbing of Saints. Those results keep Leinster, the four-time champions, on course to secure a home knockout fixture despite the loss of Jonathan Sexton to a knee injury.
Jerome Kaino's Toulouse also remain unbeaten, along with Leinster, Exeter and Ulster, after securing repeat successes over Montpellier. Unlike last week, this time Toulouse had to come from behind away from home to win 26-18.
Dave Rennie's Glasgow dug themselves a major hole after suffering a shock 12-7 home loss to La Rochelle. Rennie's men took the lead early but then let a weakened La Rochelle, missing captain Victor Vito, back into the game.
Glasgow celebrated after scoring what they believed to be the 79th minute match-winner only for Matt Fagerson to be red carded for leading with his forearm in the carry.
With that try chalked off, Glasgow must now chase maximum points from their remaining two European fixtures to have any hope of progressing.
Bundee Aki led the way for Connacht with 19 carries and five defenders beaten as they overturned an 11 point deficit in the final five minutes to steal a late 27-24 home victory over Gloucester which keeps the Irish club in contention.
Rudi Wolf's try was not enough to prevent Lyon suffering a 25-22 away defeat to Kieran Crowley's Benetton, who finally snapped their 15 game European drought. This victory was the Italian club's first since the 2014-15 season.
Matt Faddes scored from the right wing as Ulster maintained their unbeaten start against a lightweight Harlequins team that opted to rest several starters and effectively give away any remaining European hopes.
Racing 92 stayed top of their pool after defeating Welsh strugglers Ospreys and Exeter eased past Sale 35-10 despite a hail storm stop briefly stopping play.
Champions Cup results:
Clermont 52-26 Bath
Exeter 35-10 Sale
Benetton 25-22 Lyon
Leinster 50-21 Northampton
Glasgow 7-12 La Rochelle
Montpellier 18-26 Toulouse
Saracens 15-6 Munster
Connacht 27-24 Gloucester
Harlequins 10-34 Ulster
Racing 40-27 Ospreys