Hi again,

I have (stupidly) tried to copy two slices in central region (one for each lead). After 3 hours, the memory blows up. My workstation has 128Gb DDR4 memory. (kwant is compiled against mumps 5.0.1 and multithreading is working)

This is not probably not normal. I don't think reducing the problem size by 50% is
going to help you; how many degrees of freedom do you have in 1 lead slice?!
i.e. what is the dimension of the matrix returned by `lead.cell_hamiltonian()`?