  As-Based Zintl compounds Ba1-xKxCd2As2 crystallized in the CaAl2Si2-type
structure (space group P3-m1) were prepared using solid-state reactions
followed by hot-pressing. We have successfully substituted K for Ba up to x =
0.08, producing hole-carrier doping with concentrations up to 1.60*1020 cm-3.
We have determined the band-gap value of non-doped BaCd2As2 to be 0.40 eV from
the temperature dependence of the electrical resistivity. Both the electrical
resistivity and the Seebeck coefficient decrease with hole doping, leading to a
power factor value of 1.28 mW m-1 K-2 at 762 K for x = 0.04. A first-principles
band calculation shows that the relatively large power factor mainly originates
from the two-fold degeneracy of the bands comprising As px,y orbitals and from
the anisotropic band structure at the valence-band maximum. The lattice thermal
conductivity is suppressed by the K doping to 0.46 W m-1 K-1 at 773 K for x =
0.08, presumably due to randomness. The effect of randomness is compensated by
an increase in the electronic thermal conductivity, which keeps the total
thermal conductivity approximately constant. In consequence, the dimensionless
figure-of-merit ZT reaches a maximum value of 0.81 at 762 K for x = 0.04.
