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Heusler compounds are a remarkable class of intermetallic materials with
1:1:1 (often called Half-Heusler) or 2:1:1 composition comprising more
than 1500 members. Today, more than a century after their discovery by
Fritz Heusler, they are still a field of active research. New properties
and potential fields of applications emerge constantly: the prediction
of topological insulators is the most recent example. Surprisingly, the
properties of many Heusler compounds can easily be predicted by the
valence electron count. Their extremely flexible electronic structure
offers a toolbox which allows the realization of demanded but apparently
contradictory functionalities within one ternary compound. Devices based
on multifunctional properties, i.e. the combination of two or more
functions such as superconductivity and topological edge states will
revolutionize technological applications. The subgroup of more than 250
semiconductors is of high relevance for the development of novel
materials for energy technologies. Their band gaps can readily be tuned
from zero to approximate to 4 eV by changing the chemical composition.
Thus, great interest has been attracted in the fields of thermoelectrics
and solar cell research. The wide range of their multifunctional
properties is also reflected in extraordinary magneto-optical,
magnetoelectronic, and magnetocaloric properties. The most prominent
example is the combination of magnetism and exceptional transport
properties in spintronic devices. To take advantage of the extremely
high potential of Heusler compounds simple rules for the understanding
of the structure, the electronic structure and the relation to the
properties are reviewed. (C) 2011 Elsevier Ltd. All rights reserved.
