Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Thermoelectric transport in the layered Ca$_3$Co$_{4-x}$Rh$_x$O$_9$
  single crystals   We have examined an isovalent Rh substitution effect on the transport
properties of the thermoelectric oxide Ca$_3$Co$_{4}$O$_9$ using
single-crystalline form. With increasing Rh content $x$, both the electrical
resistivity and the Seebeck coefficient change systematically up to $x=0.6$ for
Ca$_3$Co$_{4-x}$Rh$_{x}$O$_9$ samples. In the Fermi-liquid regime where the
resistivity behaves as $\rho=\rho_0+AT^2$ around 120 K, the $A$ value decreases
with increasing Rh content, indicating that the correlation effect is weakened
by Rh $4d$ electrons with extended orbitals. We find that, in contrast to such
a weak correlation effect observed in the resistivity of Rh-substituted
samples, the low-temperature Seebeck coefficient is increased with increasing
Rh content, which is explained with a possible enhancement of a pseudogap
associated with the short-range order of spin density wave. In high-temperature
range above room temperature, we show that the resistivity is largely
suppressed by Rh substitution while the Seebeck coefficient becomes almost
temperature-independent, leading to a significant improvement of the power
factor in Rh-substituted samples. This result is also discussed in terms of the
differences in the orbital size and the associated spin state between Co $3d$
and Rh $4d$ electrons.

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The categories of this paper are: supr-con
21
The categories of this paper are: adap-org
26
The categories of this paper are: bayes-an
10
The categories of this paper are: q-bio
23
The categories of this paper are: solv-int
1
The categories of this paper are: cs
24
The categories of this paper are: dg-ga
13
The categories of this paper are: quant-ph
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The categories of this paper are: atom-ph
14
The categories of this paper are: math-ph
2
The categories of this paper are: math
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The categories of this paper are: cmp-lg
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The categories of this paper are: q-alg
20
The categories of this paper are: acc-phys
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The categories of this paper are: mtrl-th
15
The categories of this paper are: nucl-ex