Orbital symmetry of a triplet pairing in a heavy Fermion superconductor UPt3

The orbital symmetry of the superconducting order parameter in UPt3 is iden tified by evaluating the directionally dependent thermalconductivity and ul trasound attenuation in the clean limit and compared with the existing data for both basal plane and the c-axis of a hexagonal crystal. The resulting two component orbital part expressed by (lambda(x)(k), lambda(y)(k)) is com bined with the previously determined triplet spin part, leading to the orde r parameter of either the nonunitary bipolar state of the form: d(k) = (b) over cap lambda(x)(k) + i (j) over cap lambda(y)(k) or the unitary planar s tate of the form: d(k) = (b) over cap lambda(x)(k) + (j) over cap lambda(y) (k) where (b) over cap perpendicular to (j) double under bar = (c) over cap , or (a) over cap with the hexagonal unit vectors (a) over cap, (b) over ca p, and (c) over cap. The d vector is rotatable in the plane spanned by (a) over cap and (c) over cap perpendicular to (b) over cap under weak applied c-axis field because of the weak spin-orbit coupling. Experiments are propo sed to distinguish between the equally possible these states.