Evidence of surface superconductivity and multi-quanta vortex states in   a weakly-pinned single crystal of Ca3Ir4Sn13
  We report here the observation of anomalous paramagnetic signal(s) in the isofield field-cooled cool-down magnetization scans (MFCC(T)) recorded for a single crystal of a low Tc superconductor Ca3Ir4Sn13. Novel features emanating from the MFCC(T) response include an oscillatory magnetization behaviour below Tc and a rich multiplicity (non-uniqueness) in magnetization ranging from diamagnetism to paramagnetism at a given H, T value. The metastability in MFCC(T) has been ascribed to non-unique coexistence of multi-quanta vortex states and single quantum (Abrikosov) vortices. Additionally, the isothermal M(H) scans recorded across a short window of temperature just below Tc show evidence for only the multi-quanta vortex states in the domain of surface superconductivity, with no fingerprint(s) of pinned Abrikosov lattice. 
Santosh Kumar, Ravi P. Singh, A. Thamizhavel, C. V. Tomy, and A. K.   Grover
cond-mat.supr-con