Shallow-band superconductors: pushing superconductivity types apart
  Magnetic response is a fundamental property of superconducting materials, which helps to distinguish two superconductivity types: the ideally diamagnetic type I and type II, which can develop the mixed state with Abrikosov vortices. We demonstrate that multi-band superconductors with one shallow band, that have recently attracted much attention for their high critical temperatures and unusual properties, often stay apart of this simple classification. In a wide range of microscopic parameters such systems fall into the inter-type or transitional interval in between the standard types and display unconventional mixed state configurations. 
S. Wolf, A. Vagov, A. A. Shanenko, V. M. Axt, J. A. Aguiar
cond-mat.supr-con