Heidi Klum talks to Katie Couric

Supermodel Heidi Klum is to open up about her marriage split from Seal in her first sit-down TV interview since their January break-up on Wednesday.

The German star has agreed to talk candidly about her marriage to and divorce from the singer on US newswoman Katie Couric's new daytime show, and she'll reveal that the union wasn't as happy as people thought it was.

"People always saw us, like, laughing and smiling, but it's not always like that," she said.