  We report on the investigation of the scattering properties between the
ground state $^1S_0$ and the metastable state $^3P_0$ of the fermionic isotope
of $^{171}$Yb. We successfully measure the $s$-wave scattering lengths in the
two-orbital collision channels as $a_{eg}^+=225(13)a_0$ and
$a_{eg}^-=355(6)a_0$, using the clock transition spectroscopy in a
three-dimensional optical lattice. The result shows that the interorbital
spin-exchange interaction is antiferromagnetic, indicating that $^{171}$Yb atom
is a promising isotope for the quantum simulation of the Kondo effect with the
two-orbital system.
