John Higgins made only the 11th 147 break at a World Championship to keep alive his hopes of reaching the Crucible quarter-finals.
The 2019 finalist, who trailed 5-3 overnight, made a strong start to the morning session in his match with Kurt Maflin and reduced the deficit to one.
His Norwegian opponent responded with the next frame before he moved three ahead after a break of 97.
But four-time world champion Higgins hit back in the final frame of the session with a sparkling maximum, the first achieved at the Sheffield venue since Stephen Hendry in 2012.
It is the 10th 147 the Scot has made in his career, but he trails Marflin 7-5, while Mark Selby is 3-1 up against Noppon Saengkham.