For any perfect field k a triangulated category of K-motives DK eff − (k) is constructed in the style of Voevodsky's construction of the category DM eff − (k). To each smooth k-variety X the K-motive M K (X) is associated in the category DK eff − (k) and K n (X) = Hom DK eff − (k) (M K (X) [n], M K (pt)), n ∈ Z, where pt = Spec(k) and K(X) is Quillen's K-theory of X.where pt = Spec(k) and K(X ) is Quillen's K-theory of X . Thus Quillen's K-theory is represented by the K-motive of the point.The spectral category K is of great utility in authors' paper [3], in which they solve some problems related to the motivic spectral sequence. In fact, the problems were the main motivation for constructing the spectral category K and developing the machinery of K-motives.Throughout the paper we denote by Sm/k the category of smooth separated schemes of finite type over the base field k.
PRELIMINARIESWe work in the framework of spectral categories and modules over them in the sense of Schwede-Shipley [12]. We start with preparations.Recall that symmetric spectra have two sorts of homotopy groups which we shall refer to as naive and true homotopy groups respectively following terminology of [11]. Precisely, the kth naive homotopy group of a symmetric spectrum X is defined as the colimit π k (X ) = colim n π k+n X n .Denote by γX a stably fibrant model of X in Sp Σ . The k-th true homotopy group of X is given bythe naive homotopy groups of the symmetric spectrum γX . Naive and true homotopy groups of X can be considerably different in general (see, e.g., [6,11]). The true homotopy groups detect stable equivalences, and are thus more important than the naive homotopy groups. There is an important class of semistable symmetric spectra within whichπ *isomorphisms coincide with π * -isomorphisms. Recall that a symmetric spectrum is semistable if some (hence any) stably fibrant replacement is a π * -isomorphism. Suspension spectra, Eilenberg-Mac Lane spectra, Ω-spectra or Ω-spectra from some point X n on are examples of semistable symmetric spectra (see [11]). So Waldhausen's algebraic K-theory symmetric spectrum, which we shall use later, is semistable. Semistability is preserved under suspension, loop, wedges and shift.A symmetric spectrum X is n-connected if the true homotopy groups of X are trivial for k n. The spectrum X is connective if it is (−1)-connected, i.e., its true homotopy groups vanish in negative dimensions. X is bounded below if π i (X ) = 0 for i ≪ 0. Definition 2.1. (1) Following [12] a spectral category is a category O which is enriched over the category Sp Σ of symmetric spectra (with respect to smash product, i.e., the monoidal closed structure of [6, 2.2.10]). In other words, for every pair of objects o, o ′ ∈ O there is a morphism symmetric spectrum O(o, o ′ ), for every object o of O there is a map from the sphere spectrum S to O(o, o) (the "identity element" of o), and for each triple of objects there is an associative and unital composition map of symmetric spectra O(o ′ , o ′′ ) ∧ O(o, o ′ ) → O(o, o ′′ )....