There are several different time series for the Umlaufrendite, depending upon which underlying you use.
Here you will find an <a href="http://www.bundesbank.de/statistik/statistik_zeitreihen.php">overview</a>.
The yield for Eurex deliverable products are then selected via "Renditen und Indizes deutscher Wertpapiere", and "WX3950".
Looks like I picked the wrong underlying in the first post.
Hth
Bernd Kuerbs