The Max Planck Institute for Nuclear Physics has a number of open post-doctoral research positions in gamma-ray astronomy for candidates with experience in particle physics, astroparticle physics or high-energy astrophysics:

https://www.mpg.de/17191504/post-doctoral-research-associate-m-f-d1

More about the division:

https://www.mpi-hd.mpg.de/mpi/en/research/scientific-divisions-and-groups/non-thermal-astrophysics

and the city:

https://www.heidelberg.de/hd,Len/300652.html

and the Max Planck Society:

https://www.mpg.de/en