Na2.8Cu5Sn5.6: A crystalline alloy featuring intermetalloid (1)(∞){Sn(0.6@Cu(5)@Sn(5)} double-walled nanorods with pseudo-five-fold symmetry.

The title phase is prepared by the reaction of elemental Na with a preformed Cu—Sn alloy with an overall Na:Cu:Sn ratio of 3.0:5.0:5.6 (Ta ampule, 800 °C, 20 h).