Hi, I have found my mistake. From my background I expected to have a separate look on electron-like and hole-like quasiparticles in the superconductor. However, Kwant is not able to distinuish between those in the superconductor lead since no conservation law is defined for this lead. This is also mentioned in the documentation, but I have missed it until this morning.
Thank you for your help anyway. Markus
