here) and in Poul Anderson's first future history (here). In Anderson's second future history, Dominic Flandry defeats Cerdic in a sword fight here. Is there any other single combat in Anderson's works?
In SM Stirling's A Meeting At Corvallis (New York, 2007), Chapter Twelve, Lord Bear defeats a Protectorate knight in single combat before a battle. Circumstance has allowed life-long role-play:
"'You do me great honor in meeting me lance to lance, Lord Bear!' the young knight said, grinning from ear to ear." (p. 318)
For comparison, here are examples of single combat from three other works:
in Robin And Marian, Robin Hood (Sean Connery) defeats the Sheriff of Nottingham (Robert Shaw);
in From Russia, With Love, James Bond (Sean Connery) defeats Donovan Grant (Robert Shaw);
in Stieg Larsson's Millennium Trilogy, when Lisbeth Salander is attacked in an empty warehouse by her massive, murderous half-brother, she staples his feet to the floor, exits the warehouse, phones a biker gang to tell them where they can find him, watches them enter the warehouse, phones the police to tell them where they can find the biker gang, watches the police arrive and hears gun-fire from a safe distance. (Not quite single combat but nifty.)
Addendum, 13 Apr 2017: Single combat between the King of Ys and his Challengers, of course.