  An experimental technique of x-ray fluorescence holography for investigating
valence-selective local structures was established by employing the incident
x-ray energy at a characteristic one near an x-ray absorption edge, and it was
adopted to discriminate environments around Yb2+ and Yb3+ ions in a YbInCu4
valence transition material below and above the transition temperature of 42 K.
The reconstructed images of the neighboring atoms around Yb3+ show a fcc
structure as observed by diffraction experiments, whereas those around Yb2+
have curious cross (+) features, indicating a positional shift of the centered
Yb2+ ions from the fcc lattice point.
