Introduction

Abstract

Compounds of transition-metal element and group-14 element with composition ratio of 1:1 sometimes crystallize into a so-called B20-type structure with noncentrosymmetric space group $P2_13$. Those compounds are named to be “B20-type compounds” after their crystal structure. Their various interesting physical properties have been a source of extensive research activities for almost half a century, offering new research areas as represented by discovery of magnetic skyrmions in chiral-lattice magnets [7, 31]. This thesis is devoted to electrical and thermal transport experiments performed on 3d-transition-metal germanium compounds with the B20-type crystal structure, whose physical properties have been scarcely investigated. Our findings in the germanide system are not just to confirm the physics already revealed in other B20-systems, but explore new insights and phenomena in chiral-lattice compounds. In this Chapter, we review basic properties of B20-type compounds, i.e., their crystal structure and characteristic electronic/spin structures, for better understanding of novel transport properties emerging in the germanide system.