Abstract: Perovskite related compound of the present invention have layered structures in which perovskite units and A-rare earth structure units are alternately arranged. The reduced cell parameters ar-cr and ?r-?r and the reduced cell volume Vr are within the following ranges: ar=6.05±0.6 ?, br=8.26±0.8 ?, cr=9.10±0.9 ?, ?r=103.4±10°, ?r=90±10°, ?r=90±10°, and Vr=442.37±67 ?3. At least one of the reduced cell parameters ar-cr can be m/n times as large as the aforementioned values, where m and n are independent natural numbers, the square roots of 2 or 3 or integral multiples thereof. Values of ar, br and cr can be replaced with one another, or values of ?r, ?r and ?r can be replaced with one another.