Comment on "Enhanced two-dimensional properties of the four-layered   cuprate high-Tc superconductor TlBa-2Ca-3Cu-4O-y"
  We reanalyze published magnetization data and demonstrate that the conclusion of the original authors, claiming enhanced two-dimensional properties of the cuprate superconductor Tl-1234, is not supported by the experimental results. Our analysis shows that the magnetic field dependence of the mixed-state magnetization for this particular sample is amazingly close to the results of numerical calculations by E. H. Brandt for an ideal vortex lattice without fluctuations. This good agreement between experiment and theory allows for the evaluation of the absolute values of the upper critical field. 
I. L. Landau and H. R. Ott