[Yello] Yello & Kraftwerk

Hi everyone! At a file sharing program (known as Kazaa) I searched for Yello songs (in hope of finding some rare tracks). I came over some songs which were supposed to be made by Kraftwerk and Yello. The songs were called Running Two, Running One, Supermarket and Time Operator. I can't find them in any Kraftwerk (or Yello) discography. Ofcourse, these songs may belong to another artist, but they had a bit of Yello and Kraftwerk in them. Do any of you know something about this? Chris