We present evidence of type-I superconductivity in single crystals of ScGa3
and LuGa3, from magnetization, specific heat, and resistivity measurements: low
critical temperatures Tc = 2.1-2.2 K; field-induced secondto first-order phase
transition in the specific heat, critical fields less than 240 Oe; and low
Ginzburg-Landau coefficients {\kappa} approx 0.23 and 0.30 for ScGa3 and LuGa3,
respectively, are all traits of a type-I superconducting ground state. These
observations render ScGa3 and LuGa3 two of only several type-I superconducting
compounds, with most other superconductors being type II (compounds and alloys)
or type I (elemental metals and metaloids).Comment: 5 pages, 6 figure
