Dear Christoph, thank you for your help. Now I have the following question: I manually set leads, how to connect them to my sys? sys.attach_lead () is not suitable for my case . That's what I have: sys = kwant.Builder() left_sequence = [lat(-90.26501, 13.2107), lat(-91.60269, 12.67463), lat(-91.59045, 11.58774), lat(-90.26237, 11.08828), lat(-90.26083, 10.04835), lat(-91.58949, 9.55088), lat(-91.58643, 8.46444), lat(-90.25538, 7.968154), lat(-90.25217, 6.928836), lat(-91.58071, 6.431348), lat(-91.57723, 5.345146), lat(-90.24561, 4.849877), lat(-90.24225, 3.810792), lat(-91.57085, 3.31342), lat(-91.56733, 2.2273), lat(-90.23556, 1.732352), lat(-90.23221, 0.6933518), lat(-91.56081, 0.19601), lat(-91.55732, -0.8900915), lat(-90.22549, -1.384972), lat(-90.22213, -2.423986), lat(-91.55071, -2.921435), lat(-91.5472, -4.007565), lat(-90.21539, -4.502484), lat(-90.21201, -5.541591), lat(-91.54037, -6.039403), lat(-91.53681, -7.125625), lat(-90.20502,-7.620638), lat(-90.20139, -8.659995), lat(-91.52917, -9,158857), lat(-91.52507, -10.24531), lat(-90.1931, -10.74025), lat(-90.18774, -11.7802), lat(-91.51251, -12.28222), lat(-91.51754, -13,36915), lat(-90.17627, -13.9026)] left_lead = kwant.builder.BuilderLead(sys, left_sequence) right_sequence = [lat(-41.91176, 13.2618), lat(-40.57049, 12.72834), lat(-40.57551, 11.64143), lat(-41.90027, 11.13939), lat(-41.8949, 10.09944), lat(-40.56293, 9.604507), lat(-40.55882, 8.518044 ), lat(-41.88659, 8.019171 ), lat(-41.88295, 6.979813), lat(-40.55117, 6.484797), lat(-40.5476, 5.398573), lat(-41.87595, 4.900758), lat(-41.87258, 3.861642), lat(-40.54078, 3.36673), lat(-40.53728, 2.280592), lat(-41.86583, 1.783134), lat(-41.86248, 0.7441266), lat(-40.53065, 0.2492565), lat(-40.52715, -0.8368476), lat(-41.85576, -1.334199), lat(-41.85238, -2.373199), lat(-40.5206, -2.868142), lat(-40.51707, -3.954266), lat(-41.84566, -4.451642), lat(-41.8423, -5.490723), lat(-40.51068, -5.985983), lat(-40.50717, -7.072186), lat(-41.83571, -7.56968), lat(-41.8325, -8.609), lat(-40.50143, -9.105271), lat(-40.49837, -10.19172), lat(-41.82703, -10.68919), lat(-41.82547, -11.72912), lat(-40.49739, -12.22857), lat(-40.48512, -13.31546), lat(-41.82278, -13.85154)] right_lead = kwant.builder.BuilderLead(sys, right_sequence) С уважением, Татьяна Григоренко