Super-de Sitter and alternative super-Poincar\'e symmetries
  It is well-known that de Sitter Lie algebra $\mathfrak{o}(1,4)$ contrary to anti-de Sitter one $\mathfrak{o}(2,3)$ does not have a standard $\mathbb{Z}_2$-graded superextension. We show here that the Lie algebra $\mathfrak{o}(1,4)$ has a superextension based on the $\mathbb{Z}_2\times\mathbb{Z}_2$-grading. Using the standard contraction procedure for this superextension we obtain an {\it alternative} super-Poincar\'e algebra with the $\mathbb{Z}_2\times\mathbb{Z}_2$-grading. 
V.N. Tolstoy
hep-th