  We have recently proposed a theoretical model for superconductors endowed
with two distinct superconducting phases, described by two scalar order
parameters which condensate at different critical temperatures. On analyzing
the magnetic behavior of such systems, we have found some observable
differences with respect to the case of ordinary Ginzburg-Landau
superconductors. In particular, at low temperature the London penetration
length is strongly reduced and the Ginzburg-Landau parameter k becomes a
function of temperature. By contrast, in the temperature region between the two
phase transitions k is constant and the system is a type-I or a type-II
superconductor depending on the ratio between the critical temperatures.
