1) what was never clear to me was if the resistivity of an infinitesimal volume element of superconductor is strictly a function of temperature, and the norm of

1) what was never clear to me was if the resistivity of an infinitesimal volume element of superconductor is strictly a function of temperature, and the norm of the magnetic field, or also of the direction of current with respect to the direction of the magnetic field? near the critical current density, or even before, will the resistance depend on the direction of current? 2) while a general bulk high current superconductor is limited in currentcarrying capacity this way, most of the time one is not interested in sending current one way, but also completing the circuit and getting current back the opposite way. Why can they not make power distribution cables with indefinite currentcarrying capacity the following way: consider a "multilayer" coaxial cable where the conductors are superconductors, and to prevent a magnetic field from arising the layers have alternating current directions, so that in any layer the net magnetic field is below the critical magnetic flux? (this would only be for power distribution, since this can't be used to build stronger superconductive electromagnets). The total current would be the sum of all the even, or of all the odd coaxial layers (the 2 sums are identical since they complete a circuit...) in essence co-locate the 2 problematic magnetic fields such that they cancel... A superconductive "humbucker"