I think that's it...everything agrees quite well with your photo below:

     

...e.g. color pattern, shape of antennal segments, long white setae, tarsal pads, size, general habitat & location (desert scrub at base of mountains east of the Sierra Nevada).

I added a link to the info page for the 1921 Aulicus paper by C. Schaeffer where A. antennatus was originally described (type locality: Palm Spring, CA). The relevant part of his key is reproduced below (with characters visible in my photos highlighted in green and characters that clearly don't hold there in red). This does appear to go to A. antennatus:

1) Head red, prothorax bluish-black at middle, red at sides.....2
1') Head and prothorax entirely black or black bluish.....3
3) Antennae with joints six to eight in the male, or seven and eight in the female, triangularly dilated and intermediate in size between the preceding joints and the club, more strongly pronounced in the male than in the female........8
3') Antennal club abruptly three-jointed........4
8) Body below and legs entirely metallic blue; sutural vitta above the median fascia as wide or wider than the red humeral space; humeral spot absent; fifth ventral segment rather deeply arcuate-emarginate and last dorsal segment rounded at apex in the male, the latter in the female narrowly, subtriangularly emarginate at apex. The inner claw of the front tarsi toothed in the male......antennatus
8') [No opposing choice given here in Schaeffer's key. Since this was the final couplet of the key, and all species discussed in the paper appear in the key, it seems the lack of an opposing choice here was simply an unconventional stylistic device rather than an error in the construction of the key.]
The step at couplet 3) seems critical to me...I think I can see what is meant by "Antennal club abruptly three-jointed" in other current BugGuide Aulicus posts, for instance those below:

             

In contrast to those, our two posts do exhibit a more gradual transition from the proximal antennal segments to the distal 3 club segments. And I do think I can see (at least a suggestion of) "triangular dilation" on the inner edges of segments 6-8 in my 1st photo (which seems more pronounced than in your post...so I guess mine is a male and yours a female? Also the fore-tarsal pads seem more pronounced in mine, no?)

I think the lack of clearly metallic-blue legs is not especially consequential...Schaeffer's actual write-up of A. antennatus uses the descriptor "bluish black" instead of the phrase "entirely metallic blue" he used in couplet 8) of the key. Also, his detailed description of the antennal segment shapes in the male seems to fit my photo extremely well (to see what I mean, "zoom-in" on the full-size image by pressing "cntl-+" repeatedly). And Schaeffer emphasizes antennal characters as important here (reflected in his choice of epithet).