Novak Djokovic was at the centre of another Australian Open row on Monday while Jannik Sinner needed medical attention in fierce heat to battle into the quarter-finals and Iga Swiatek won easily.

But American teenage qualifier Learner Tien's fairytale run is over after he suffered a thigh problem in a four-set defeat to Italy's Lorenzo Sonego.

With temperatures rising above 30 Celsius (86 Fahrenheit) for a second successive day, Ukraine's Elina Svitolina beat Veronika Kudermetova -- then declined to shake the Russian's hand.

But Svitolina's husband, the 38-year-old Frenchman Gael Monfils, retired from his match in the last 16.

Five-time major champion Iga Swiatek thrashed "lucky loser" Eva Lys 6-0, 6-1 in her bid to win a maiden Melbourne crown.

The 24-time Grand Slam champion Djokovic on Sunday refused to do a routine on-court interview after beating Jiri Lehecka to set up a quarter-final blockbuster against Carlos Alcaraz.

Afterwards he said it was in protest at Tony Jones, a top sports presenter with........

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