This paper presents a brief review on the reported anisotropic properties of
MgB2, in the superconducting state (e.g. upper critical field Hc2, field
penetration depth, coherence length, energy gap) as well as in the normal state
(e.g., magnetoresistance, compressibility, thermal expansion). So far, the
reported results have been obtained using aligned crystallites, c-axis oriented
thin films and sub-millimeter crystals. Since impurity scattering affects
directly the gap anisotropy it could be one of the main reasons for the
different values observed in the Hc2 anisotropy ratio, ranging between 1.3 and
2.6.Comment: 16 pages, 5 figures. To appear as a chapter in "Studies of High
Temperature Superconductors", Vol. 38, p. 263, ed. A.V. Narlikar (Nova Sci.
Publ., New York, 2001
