First-Order Reorientation of the Flux-Line Lattice in CaAlSi
  The flux line lattice in CaAlSi has been studied by small angle neutron scattering. A well defined hexagonal flux line lattice is seen just above Hc1 in an applied field of only 54 Oe. A 30 degree reorientation of this vortex lattice has been observed in a very low field of 200 Oe. This reorientation transition appears to be of first-order and could be explained by non-local effects. The magnetic field dependence of the form factor is well described by a single penetration depth of 1496(1) angstroms and a single coherence length of 307(1) angstroms at 2 K. At 1.5 K the penetration depth anisotropy is 2.7(1) with the field applied perpendicular to the c axis and agrees with the coherence length anisotropy determined from critical field measurements. 
P.K. Biswas, M.R. Lees, G. Balakrishnan, D.Q. Liao, D.S. Keeble, J.L.   Gavilano, N. Egetenmeyer, C.D. Dewhurst, and D.McK. Paul
cond-mat.supr-con cond-mat.mtrl-sci cond-mat.str-el