On the verge of short D-D distances in RNiIn deuterides

► Optimized method of hydrogenation the RTIn hexagonal compounds was developed. ► RNiInDx (R = Gd-Er, x > 1.3) deuterium-rich phases were synthesized. ► Structural properties at ambient and elevated temperatures were investigated. ► There are no short D-D distances as was evidenced for (La-Nd)NiIn compounds.