   function   X=sMat(x)
%  Use the isometry version
tn=length(x);
n=floor(sqrt(2*tn));
E=ones(n);
indsu=find(triu(E,0));
indsuu=find(triu(E,1));
X=zeros(n);
X(indsu)=x;
v=diag(X);
X(1:n+1:end)=zeros(n,1);
X(indsuu)=X(indsuu)/sqrt(2);
X=X+X';
X=X+diag(v);
