A spin state transition in a square planar coordinated iron was found in SrFeO₂ and Sr₃Fe₂O₅ under high pressure. This transition occurs as a consequence of enhanced Fe-Fe direct interactions between adjacent face-to-face FeO₄ square planar units. We also found a pressure-induced structural transition in Sr₃Fe₂O₅, which is viewed as a B1（NaCl structure） to B2（CsCl structure） structural transition. Such a B1-B2 structural transition generally occurs in intergrowth system consisting of rock-salt blocks and square-planar blocks, as found in A₂MO₃ （A＝Ca, Sr; M＝Cu, Pd）. An empirical relation between the structural transition pressure P_s and the ionic radius for the binary system holds well for the intergrowth structure, which indicates that the square-planar block is highly compressible along the out-of-plane direction.

We have determined the crystal structure at 0.48 Å resolution of high-potential iron-sulfur protein, HiPIP, which is a small soluble protein playing as an electron carrier in photosynthetic bacteria. The ultra-high resolution structure of HiPIP enabled us to perform charge-density analyses where distributions of valence electrons were clearly visualized as the first case of metalloproteins. A topological analysis of the charge density provided electronic structure information for the iron-sulfur （Fe₄S₄） cluster as well as the peptide portion.

In-situ synchrotron diffraction experiments were conducted in order to clarify the formation process of α'-martensite from the γ-phase induced by external strain, combined with Lorentz transmission electron microscopy （TEM） and high-resolution TEM observations. Lorentz TEM observation revealed that α'-martensite exist near the defect structures such as dislocations and stacking faults in the parent γ-phase. In addition, it is clearly demonstrated that ε-martensite with hexagonal symmetry appears as an intermediate phase during the plastic deformation of SUS304 stainless steel. Our experimental results suggested that the interfaces between twin structures of the γ-phase presumably play a crucial role in the formation of ε-martensite.

本誌58巻4号掲載の最近の研究から「新物質A（TiO）Cu₄（PO₄）₄（A＝Ba,Sr）における結晶カイラリティの強度とドメイン構造の相関」（pp.174-179）およびクリスタリット（p.195）について，以下の誤りがございました．訂正いたします．

（1）p.174，左欄，下から3行目：

 （誤）そのうち実に65種がカイラルな空間群である．

→（正）そのうち実に65種の空間群においてカイラルな結晶構造が許される．

（2）p.175，右欄，7行目：

 （誤）正方晶カイラルな空間群→（正）正方晶系の空間群

（3）p.195，右欄，14行目：

 （誤）結晶構造の対称性を記述する全230種の空間群のうち，65種が回映軸をもたないカイラルな空間群である．

→（正）結晶構造の対称性を記述する全230種の空間群のうち，65種が回映軸をもたない空間群である．