Novel superconducting niobium beryllide Nb$_3$Be with A15 structure

New niobium beryllide Nb$_3$Be with A15 structure and lattice parameter $a=0.5187\pm 0.0007$ nm, coexisting (3-5%) with a tetragonal phase, presumably, of an ordered solid solution with parameters $a=0.5414\pm 0.0008$  nm and $c=0.6378\pm 0.0009$ nm, was synthesized by thermal treatment (875-110$^{\circ}$ C) of amorphous film coatings containing 26.8-32.4 at.% Be and formed from short-period Nb and Be layers by magnetron sputtering. The domain of existence of the Nb$_3$Be phase and the critical superconducting transition temperature (10.0 K and a transition width of 2.5 K) were determined and the X-ray structural data for structure identification were obtained.