After testing several materials, I'm happy with Polymaker PolyMide PA6-CF with generous applied dimafix on the build plate + brim.
If also strenght between the layers is needed, especially in Z-direction, I temper at 250°C in plaster powder (instead of ground salt)
Tensile strenght at break rises to 80 N/mm². For those who are interested in details, see attached test report.
20201223_Biegezugprobe_messprotokoll.pdf